Mom refuses to go anywhere or do anything. Her response to every suggestion made by me, her primary caregiver, is “NO.” Suggestions?

Well the first thig with dementia is that you do not give options.
If you say "Mom, do you want to go for a ride?" she will say "no"
If you say "Mom, we are going for a ride." then you get her into the car and go get lunch or an ice cream or just drive around.

The fewer choices and options you give the better.

It is typical in the later stages of dementia to sleep 20+ hours a day but if mom was able to do a 3 hour car ride and manage to get around a casino for 2 hours that does not sound like later stage of dementia.

I don't understand your drive to make your mother more active if she doesn't wish to be so? It seems like she is perfectly able to enjoy those few things she still enjoys. At some point that needs to be enough.

Be grateful that sister is willing to take mom out! Use that time for yourself.

A dementia patient does not need to be kept active unless she herself wishes it. Often we project our own needs onto them. If that might be the case, find a sitter to stay with mom while she sleeps for 20 hours. Then you and sister can go to a casino and have a fun day. Bingo!

Why do you want to keep a woman with dementia "active" when she wants to sleep all day? How is that going to help her, do you think? Projecting your wishes onto her isn't a wise idea. Let mom call the shots now, she's earned that right. Ask her if she wants to go to the casino or out for a meal. If the answer is no, respect her decision.

How did your rister approach Mom to get her out? Did she ask or did she tell. "Mom, I am here to take you for a ride to the casinos." I found with my Mom staff would ask "Do you want to...". Like a toddler the answer would be no. If it was " Come on P we are going to the toilet" She would go.

DH and I are in our late 70s and find we are slowing down. Can't imagine what our 80s will be like. You don't say how old Mom is and how advanced her Dementia is? I will bet that day out did her in for a couple of days.

Why do you want to force her to go somewhere. I do not consider myself old only 67 but to be honest, I don’t like to go out either. I don’t like dealing with traffic or rude people. If I go out with a friend I usually have a good time, but I could’ve had just a good time staying at home.

How old is your Mom? Does she have any other health issues?

Sometimes we adult children project onto our elderly parents how we think they should be living.

I stopped cajouling my LO. She gets to live like she wants, eat what she wants, etc.

watch some videos by Teepa Snow and read the book "the 36 hour day".
It taught me so much as i was caring for my Mom from 2020-2022. I leaned so much about empathy , compassion and imagining being in that person's place. How would I want to be treated.
It was the hardest thing I ever did and the most important.
Mom passed away at 99-1/2.

a hug of compassion for you.

Not sure why you want to force your mom to go out and be active? Let her be. She doesn't need to be treated like a child. Your mom can decide if she wants to go somewhere or not. Please don't push her.

From my experience with my 99year old MIL who lives with us, she does not process questions. She says no because she does not really know what we want. I have to tell the medical people to not ask questions because she cannot understand. I do not know why. One day a nurse ask her “What is your name?” She said she did not know. I told the nurse to tell her to say her name. The nurse said “Tell me your name.” She stated her name quick as a wink. Just get the wheel chair out and put her in it to go for a walk. Put the table in front of her and set down cards, pictures, magazines or what ever. Put towels to fold in a basket and sit by her and hand her towels…she will fold - you don’t have to say anything.
Sing songs she used to know, The only thing that did not work is giving a paint brush, paint, and paper, Even doing it with her was too overwhelming for her to try.. too many steps…she did not comprehend and it was too much.