What is the right answer?

Telling her that "XXX" is dead will not help. She will forget, may get upset at the "news" or maybe not believe what she is told.
Telling her that "we can't go today" or "XXXX is not home today" or "we have other plans, we were going to go for a walk or a drive today"
Yes she will get angry but that is because she is not getting what she wants at the moment.
Is there anything that she likes? A particular snack? A favorite movie or song? Use anything you can to redirect the conversation.

As you have come to see, your MIL's reality is not yours. Her dementia has affected how she thinks and what she believes. The proper response may be different for different people living with dementia. Some will accept the fact that their relatives are dead without any specific emotional reaction. Others may react completely differently- cry, or deny their LO is gone. The honest reply of her mother being deceased doesn't seem to work. The preferred approach is to validate the fact that she thinks her mother is still alive. Your husband's replies, “maybe tomorrow”, may seem ridiculous to you, but it may be a response your MIL can accept. In a sense, he is “playing along to appease her”, but if that momentarily satisfies her, it's what's needed. The follow up to that response is to re-direct her thoughts by suggesting getting something to drink, taking a walk, watching TV, etc.

Your MIL will continue to have delusions and hallucinations throughout her disease. I would suggest you learn how to respond to them by educating yourself. As already suggested, The “36 Hour Book” is a an excellent primer to dementia caregiving.

As for your husband, his devotion is to you. Sometimes the other spouse feels like a third wheel and begins to feel resentful. Bring your feelings to your husband's attention. Suggest that someone comes in occasionally to be with your MIL while the two of you do something together.

Traces, has your MIL been evaluated by a Geriatric psychiatrist?

Meds won't stop the repetitive questions, but they may quell the agitation and anger.

Traces109, you feel like you live in the twilight zone because you are. That said, kudos to you and your husband for providing your MIL's care. Early on in providing my dad's care, when he would ask me to take him home because his parents were waiting for him, I would explain to him that they had died decades ago. When I showed him pictures of their headstone (with him in the picture), he would get confused and sad. But, he'd soon forget and again ask me to take him home. Eventually I learned to tell him that it was too late in the day today, but that we could leave in the morning after a good night's rest and breakfast. That answer usually satisfied him, but when it didn't, then we'd go for a drive or walk "to take him home" and he would quickly tire or just forget where we were supposedly going. This was one of our routines for several years. Also, I second the recommendation for "The 36-Hour Day" book.  Best wishes to you, your husband and his mother -- this is a hard time for all of you.

Hi. I have been to counseling alone and with my husband. It didn't really help. I started looking for my own place, too bc my husband is intent on caring for his mother for as long as he can. I am turning 65 next month. I gave up my life in NJ/PA to join him in Florida. A little over a year after we got married, his mom had a stroke and came to live with us.

I'm too old to start over. I decided to stay but have detached myself from MIL's care. I limit myself to one part of the house (I work from home) so I don't get involved with her care. Once in a while I would keep an eye on her when my husband has to do something or be somewhere.

I have resigned myself to the fact that this is my life. I will retire in December and plan to vacation somewhere, on my own, for a few months.

I suggest that you read the 36 Hour Day. Yes, often the best way to answer questions about long dead parents and other relatives is to use a therapeutic white lie. My mom would often a s k about the mother and father and a sister that had passed 50 years ago when 26.

Initially I would try to straighten mom out with the truth, which was never remembered anyway and only caused renewed grief as if it was the first time she heard it. It went so far as to become an accusation of not being told at all.

Hubby is doing great as a caregiver. Let him deal with it as he sees fit, his job. If this is hard on your marriage a s it sounds like it is it may be time for counseling and exploring other living arrangements for MIL.

Have you done anything since your first post a year ago to try to figure out the best way to deal with this that will work for everyone, including you?

https://www.agingcare.com/questions/my-marriage-is-about-to-end-am-i-being-selfish-460436.htm?orderby=oldest

My mother would ask about her mother, her father. In the beginning I told her they had passed & she would take it in. But seeing her go through that again & again made me change what I was doing. Instead when she asked about a deceased person, I just started listing who was alive. She’d say, where’s mother? I’d say well, you have you brother (then his name), your son & daughter (then our names) & then I’d list the pets in the house. It distracted her & turned her focus to what she does have. Then I’d suggest we go do something or call a loved one. It made her feel better.

My mother would ask about her mother, her father. In the beginning I told her they had passed & she would take it in. But seeing her go through that again & again made me change what I was doing. Instead when she asked about a deceased person, I just started listing who was alive. She’d say, where’s mother? I’d say well, you have you brother (then his name), your son & daughter (then our names) & then I’d list the pets in the house. It distracted her & turned her focus to what she does have. Then I’d suggest we go do something or call a loved one. It made her feel better.