How do I gently communicate to a loved one that she has memory trouble?

Willpower, I have read your profile and see that you are a younger man trying to care for your grandparents. It would be helpful to know if they are living by themselves in their own home or with you, or if you are living with them.

But there's a larger issue for you, which is what you realistically want to/are able to do for them. Dementia/cognitive and physical/health issues will just keep increasing, and often there will be decline on every front, almost daily as they lose abilities to do what they used to do. IMO you can help them get transitioned into a care community (like assisted living or a nursing home) but you will first need to have a very clear picture of what their finances are. If you do not have durable Power of Attorney for them, and if they are resistant to revealing this info to you (which is quite common), your ability to help them will be limited and needlessly difficult.

Is your grandfather in better cognitive condition than your grandmother? If so, you can try to have the conversation with them that you can't be their caregiver and they need to have a plan in place. You can offer to help with certain things (and you will need to put up boundaries for this). Not sure how this conversation will go. If they both seem to have cognitive issues, and you do not have PoA for either of them, there is really only one other pathway for them and that is for you to get social services in to assess them for in-home services and allow the county to eventually take guardianship of them so that they will get taken care of. Even if they were willing to compensate you, it wouldn't be enough and it is a very stressful job that ties you 3 together for a long time without much career/financial reward and the risk of the stress having a negative health impact on you. Please read some of the thousands of posts on this forum under Caregiver Burnout from the children and grandchildren of loved ones for whom they tried to provide care.

If your grandparents have some financial means (more than just their social security checks) and at least one of them has all their mind, you could help them look into arranging a professional Power of Attorney (usually an attorney) to take care of their needs.

Caregiving often begins in small increments: some yardwork here, some grocery shopping there, bringing a meal, driving them places, finding out the bills aren't being paid, one of them falls and breaks a hip -- and before you know it you are heroically and desperately trying to juggle flaming balls but catching fire as you do. don't envy you having to make whatever decision you settle upon, but you are too young to take this fully upon yourself alone. Blessings!

Redirect, change the subject.
Don't try to tell her. Either she won't remember or she'll be angry you suggested it.
For example, "where's my computer" ---"Grandma did you get enough to eat for lunch? "
"Why does my cellphone look like this?" ---"Grandma is trashday on monday?"

Sometimes a white lie can get you there faster but it depends what you're comfortable with. "Where's my computer?" ----"It broke, so I took it to be fixed"
"why's my cellphone look like this?"----"The plan was cheaper"

I've tried to explain to my mom that her brain just doesn't work the way it used to, that it is different and it isn't her fault. She knows she has dementia, but doesn't seem to understand quite what that entails. She used to be under the impression that it would get better with time but must have come to some realization that it won't because she has stopped asking when she can come home. She will not accept that she has misplaced something - it has always been "stolen." She will not admit to making up stories of things that never really happened - "she is NOT a liar- everyone else is lying." At first I would try to reason with her but it only frustrated both of us, so now I just nod and smile or if on the phone say "oh, yes, I know."

I've seen a lot of ads for the Grandpad. Is that something you think she could use rather than a computer?

When my dad was still living and his Alzheimer’s was getting worse he said to me one day “ sometimes I think I’m going crazy.” I just told him that he wasn’t crazy, his brain had a disease, that was why he would feel that way. He actually was very relieved to hear that and was happier the rest of the day. Your grandmother on her better days is voicing that same concern in her way. You can tell her the same thing. I think using the word disease is much more acceptable to a person with dementia. I can tell you
that I fear getting Alzheimer’s and I’m sure dad did also, so I just gave it a different name for him.

Give her back her computer. Put a "child guard" on it if you're worried about scams and make sure she has no credit cards on it. But give her back her computer.

Willpower, I think that it is a losing battle and a potential war to tell someone that doesn't know that they are slipping mentally.

My dad refuses to believe it and when family has said that I told them that he has some dementia I was called a fning liar. I just let it go.

When I get questions from the dementia I just say I don't know, I can check into it or I make noises of acknowledgement and promptly forget the grumping.

Learning to not answer a question is challenging, learning to tell lies is challenging and seeing an elder deteriorate right before our eyes is challenging. It is a brutal disease for everyone involved.

Can I recommend that you start getting resources together for the time that you can no longer care for her in home. It will help you feel less overwhelmed, this is one situation where knowledge is power.

Edit: there are different kinds of dementia and different stages to each and they are not mutually exclusive, she could have more than one kind. The only thing anyone really knows is that it will get worse and just when you think that you have something figured out, the disease progresses and you are at ground zero again. Tons of helpful information here but I think that we would mostly all agree that it is an individual journey and you just have to try until you find what works best today, because tomorrow could be different. It is really hard in the beginning because they are themselves so often that you wonder if you are the one losing your mind.

I feel I have experienced what all the previous people have said. Having an expert tell them their short-comings when you can is best, because you are going to have enough battles down the road. A doctor did tell mom she had probable Alzheimer, she turned to me and said "You brought me here, just, to tell me that." I told her I took her, because there are a number of possible reasons for the cognitive decline, I was seeing. I happened to answer the phone when the doctor's office called saying she failed her driving test. I should have told them to schedule an appoint to tell her directly. She has never forgiven me for losing her license. So, even though she knew, she avoided it. I was not to use the word Alzheimer in her presence. Go to the bank and have them tell her, they have concerns about her finances, if they are willing to do that. I am now dealing with my MIL, who is denying any cognitive issues. She fabricates frequently.
As someone mentioned, it is incomprehensible how they can't think clearly at one moment and can make a rational excuse for their actions at another moment.
Experiences that have intrigued me: 1) Mom was unable to do ADLs by herself, and was incontinent. I wanted to lay flat on her back because she had abdominal pain. She could not do it. Finally, I said, "We don't need to do this!" She replied, "You are angry with me" (They are very good at picking up emotional cues). Me: "No, I just wish you could do what I ask." Her: "You know I would if I could"
2) Several years later and declined significantly, She asked my father if he was her father. Being HOH, he asked "What?" I quickly interjected that it was time to go to her Memory care facility. As we walked to the car she said "You know, I miss my Dad. I miss everything. Everything is such a mess!"
3) Mom is now mostly nonverbal, and sleeps most of the time. My Dad said in front of her "Too bad she has no idea what is going on." I told him that I do not agree with that. I believe there are times she is aware, and a good chance it is more often than I realize. I looked at her and tears had weld up in her eyes. When Dad took her hand she squeezed his hand as hard as she could and growled at him. I am sure she was trying to tell him she was angry for what he had said. When he kissed her good-bye, she giggled like a school girl. So do not write her off at any point.
I found the book 'Still Alice' very true to what I was experiencing at the time. It left me in a funk for several weeks, but I am glad I read it.
Look for the blessings in this long difficult journey.

I'm not clear with her living situation, is she living with you? Why can't you let her use the computer on her better days, with supervision?

As for her questions, this is where the therapeutic fib comes in: gee grandma, we had to take the computer in to get fixed and it isn't ready yet. The phone came with the new phone plan, it is supposed to be easier to work and was a much better deal.... The idea is to give whatever answer sounds reasonable and will satisfy her for a while, but of course she will keep asking because she won't remember.

I let Moms doctor tell her. But, this doesn't mean she will remember. You may have to tell little white lies. But then u may have to answer the question every day every day.

Give her back her computer, but alter it with child failsafes.