Why does everyone else get the joy and laughter from mom, but my sister and I get the whining and can barely talk?

You are her "safe" people. You know she hurts so she does not have to put on a "front" for you.
It is also possible that getting a phone call lifts her spirits a bit and for a time she forgets her pain.
There is a Senior Center near me that has (or had) a "phone a buddy" program for this very reason. It gives another focus for a while. (And it also served to "check in" on Seniors that may be alone.)
If you can arrange for her friends to call her every other day at a time that seems to be her worst it might help her and you.

I am going to get a bit off subject here but as mom declines it might not be wise to move her every 6 months. If it is possible mom now might do well in Assisted Living. that would give her more contact with people and activities that might help. And as her memory declines Memory Care might be a possibility.

Because you allow it?

I can not stand a whining human being and I do not hesitate to tell them to stop or I will not be listening to them because I can not understand what they are saying when they whine. Asking if they would like some bread and cheese with their whine can be effective in stopping it.

I would ask her if she would find a facility more to her liking since she is obviously so miserable in your home.

Edit: I would not say this to someone far advanced in dementia but, I would tell her that she needs to stop whining and speak in a manner that can be understood. She can control it, she has proven that, it has become habit and needs to be corrected.

This is normal human behavior at any age. If you think about it I would imagine you say mean things to your sister you would never say to strangers. We let it "all hang out" with those we most love and trust. File under "normal".

My mom, around her BINGO friends is like a 180 from the person I see.

It's a big charade and it's not hurting anyone, so why worry? Around me, she is nonstop complaining, worrying, fussing and it never stops! I took her to BINGO on Tues and she got out of the car, saw a couple of friends and went into her Southern Belle routine. Not 2 minutes had passed but what she was complaining to me about how bad her shoulders hurt.

SMH

I know I am far more 'open' with my sis than anyone else, b/c she is the one person I KNOW who loves me, even tho I am highly annoying :)

Being in pain and not complaining or finding an outlet is exhausting and adds to the pain. She can do it for a few minutes on the phone with her friends when she has her "company manners" on, but it's impossible to keep that up all the time.

I understand it's tough to listen to, but try to have some compassion for her. Her friends get the best of her, but they aren't doing any of the heavy lifting either. As the others have said, it's normal.

My daughter was an extremely colicky baby and cried for eight hours straight every single day until she was five months old. I almost lost my mind, especially because if someone came to the door, she stopped as if someone had hit an off switch on her.

Why? Because something interesting was happening that distracted her from her misery. However, if that person stayed more than about a half hour, she'd eventually fire up again and the visitor would flee, leaving me to deal with a screaming infant once again. She couldn't keep up the charade forever -- she was hurting.

I think your mom is much like my baby was -- she's hurting, and she can't help it for long.

It is unfortunately pretty normal. Most people, of all ages, are at their worst behavior when they are home and let their hair down. Starts when we're kids - how many times have we heard about the kid that is a terror is described by a sweet, helpful student in kindergarten? Sooo common.

Of course, it's very annoying for those of us who have to listen to the negativity, the whining, complaining, aches and pains, etc. etc. There's a couple of tactics you can take. Put yourself in the right frame of mind to deal with it without getting upset by it. With my mom, my hot spot is her constant repetition with telling the same darn stories over and over. When she goes to my sisters once a month for a few days, it really drives her nuts. I've told her - EXPECT the conversation to be boring. Have something to do, like dishes and have the convo in the kitchen so at least you can be productive while the convo is mind numbing.

OR if you can't take it, take someone's advice above, and set some boundaries, telling mom that you need her to speak in a normal voice, like she does when she speaks on the telephone. Not to complain or do X or Y, if you are DONE with hearing it. As long as she's not too far gone with dementia, she should be able to modify her behavior a bit.

Your mother is a guest in your home and in your sister's home. As such, she should limit her whining and complaining to a minimum or she will outstay her welcome in short order. We're advised to "show compassion" for these elders bc they're hurting, yet who's showing compassion for us who have opened our doors for them, and are likely doing our OWN fair share of hurting too?

Tell your mother, firmly but lovingly, that you cannot tolerate whining or complaining and to please let you know when she's hurting and what you can do to help. You'll reserve 30 minutes a day for complaining and carrying on, but then you'll focus on gratitude and what you feel happy for in life. Keep a gratitude list and add to it daily, every time she starts whining...make her add one thing she's grateful for to the list.

Betcha her attitude gets better when the audience no longer eats up the subject matter. Give it a try. Elders don't have a right to suck up everyone's joy because they're old and it's "normal". Create a new normal!

How lovely that you and your sister share the responsibility. I commend each of you!

Caregiving usually falls on one child.

She feels most comfortable with the two of you. She shows her best face to others. This is common for people to do.

I suppose that you could tell her to please stop whining. It may or may not help.

Have you tried walking away? I find that most times if you argue, people sometimes get defensive and argue more or in her case, whine more.

I hope you will find a viable solution soon. If not wear earplugs or listen to soothing music!

It is very common to have a LO "treat" those doing the bulk of care and oversight this way. Not necessarily the change in voice or tone, but definitely treated differently.

Have either of you tried calling mom when she is with the other sister? Does she behave the same way as when she's with you? Then that's likely how it will continue. If she treats you nicely, like those others, then it's a charade.

If at all possible, try not to "baby" her too much. Don't cater to the whining and complaining. With memory issues, she may not "learn" why, but you can still care for her and provide what she needs without jumping when she says jump.

Ever heard the expression "Familiarity breeds contempt?" It's almost like they become too used to having you around and you doing what they demand, so this is the way it is. The other expression that comes to mind is "Putting your best foot forward." This means putting on a 'mask' in a way, for those who don't live with you. There are people who will be sweet and oh so nice in the company of others, and then talk smack about them when they aren't there! IF she doesn't often see or talk to these others, there's that old chestnut "Absence makes the heart grow fonder."

My mother's typical greetings when I would visit MC were "What're you doing here?" and "Where'd you come from?" I did hear her say this one time to YB as well. OB, on the other hand, got the greeting like he was a long lost soul. The difference? I was there often. YB was, initially. OB isn't local, so his visits were few and far between! Who knows why they might do this? Maybe it's a way to encourage more visits or calls? Maybe it's just remembering all the good things, not the bad, and idealizing them.

I chose not to let it bother me. It wasn't just because of the dementia. She would often crow about how he called EVERY Sunday (emphasis hers.) It didn't matter that I called at least once/week, generally more often than that! I would sometimes give her a flip response, such as Pluto or Venus or ask her if she wanted me to leave. That was really it. She didn't follow through with it. Would it be nice to be recognized? Sure. Would my life fall apart if I'm not? Nope.

I suppose in some twisted way you could take it as a bit of a compliment - she's comfortable enough with the two of you to act "normal" vs putting on a show for the others.

From my experience when my dad had dementia...the caregivers sometimes get the bad times... he was more apt to argue or yell at me and my mom, yet anyone else, he was more polite. I. Felt hurt a lot, yet I learned a lot. It’s hard to not take words or actions personal...I have to remind myself more now that my mom has dementia. I try not to argue with her or take her words or comments personal. It’s not her, it’s the dementia.

It's always daughters that get the shirt-end of the stick. It's good that your sister shares the burden and that it's not just you alone that mom dumps on.
If you were to tell your family or mom's friends what she's like to you they would think you're crazy and just resentful. I know what that's like because I'm living it every day. My sister gets none of it. The abuse, whining, complaining, gaslighting, and misery is for me alone.
If you and your sister are going to continue caring for her in your homes, you two are going to have to learn how to ignore her. When the little girl whining starts get up and walk away. Repeat yourself twice and no more. If the same question keeps getting asked over and over again, don't answer it. She'll stop asking.
Stop catering to her every whim too. That's why she whines. And never forget that misery loves company. She wants someone to drag down with her and has two people. You nd your sister.