Are dementia patients frisky? Can dementia patients talk in stage 6 in any degree?

Butterfly, welcome!

Have you tried saying "no" and remaining seated?

She may very well understand that behaving a certain way to you will cause embarrassment and discomfort and she enjoys it.
Elderly people, even ones with dementia, have different behaviors for different people.
For example, an elder in a facility even one with dementia may be the life of the party. Engages in every activity, is very pleasant and has many friends. The moment a certain person (usually their adult child) comes in, they completely change. It becomes all about the gloom and doom, complaining, crying, and begging to go home.
I was an in-home care provider mostly to elderly for 25 years. I was a supervisor in a very upscale AL too. So, I've seen this a million times.
A friend of mine placed her mother in the AL I worked in. Every time she visited her mother started with the guilt-tripping, crying, begging, telling her that the food is so bad she's starving, you name it.

So I said to this elder in front of her daughter that not five minutes before she came in mom was up at the buffet for a third helping of food and was having a real laugh with the people at her table.
This angered her and she stopped speaking to her daughter for a stretch and took her off the visitor's list. She got over it.

I had an elderly male client with dementia years back. He also had two other female aides who worked for him. He used to say very sexually innappropriate things to me and try to get handsy with me. Not the other two. I complained to his son and my agency and they dismissed it as him having dementia and doesn't know better. I would have quit that client, but I needed the money.

One day I was doing the dishes and he put his hands on me. I turned around with a knife in my hand and pointed it at his throat. I told him that if he ever tried to touch me again it would be the last thing he ever did.
He never laid a hand on me again. He never made another innapropriate comment either.
Funny, he supposedly had dementia and didn't know what he was doing yet he somehow rememebered three days a week when I worked for him to not touch me or talk dirty.

I would suggest that if your MIL does it again, call her out on it. Make a scene and embarrass her. Then she if she ever does it again. It's likely she won't.
If she does, then she really doesn't know better and you should not visit her alone again.

I want to validate your feelings as I also wouldn’t find this funny, even if I understood that it’s the disease.

I agree that since it’s triggering something inside of her that is making her have off behaviors that are troubling, it’s probably a gift if you stop going to visit for a while, perhaps a long while.

Go to see her with husband only would be my advice here.

I would tell her that what she is saying is very inappropriate and you don't appreciate it and NO you will not turn around and show her your butt. Then I would turn to the ones that are laughing and tell them quietly they are only encouraging her so please stop. Tell them too, that it's embarrassing for you. Its like a small child.

I am with you, I would not be sitting there all day either. My limit was no more than an hour unless there was some kind of entertainment.
Bonding, you can't bond with someone with Dementia. If you hadn't bonded before the Dementia, not going to aft.

It appears that you trigger something in her. Perhaps not visiting her when you are alone would be a kindness.

If anyone asks, tell them that your presence appears to be robbing her of her dignity.

Thanks for your response to my post. Judging by what you responded to me, I wouldn’t bother going by yourself or with your husband.

If you don’t want to visit for hours with him, then don’t join him. You say that you want to show support and want to know how she is.

Ask your husband how she is. Tell him in a loving way that you care but that you aren’t able to have a pleasant visit and that you have decided not to go.

If she cries and carries on for hours while he is visiting her then surely he knows that the visits aren’t very meaningful. Why would he expect you to bond with her? She isn’t capable of bonding with you.

Maybe you could provide literature for him to read or ask a nurse or doctor to explain the situation to him.

Why is he staying for hours? He could leave after an hour or so.

The very last thing that I would do is to waste my time arguing with a person who wasn’t able to comprehend. Why torture yourself like that? You don’t sound like a woman who has an argumentative personality to me.

Stay home or visit a friend while he is with his mom. When he returns say, “Hi, honey. How’s your mom?”

Best wishes to you and your family.

"I'll show you mine if you show me yours. You go first."

My Daddy talked about sex when he was very sick. I just told him that was not a great subject to talk to me about and then I would change the subject. When MIL does this just tell her it is not nice to ask me to do that or say those things. Then change the subject to flowers, weather, or tv shows.

If you’re uncomfortable seeing her on your own, then don’t go alone. What do you do when she says these things to you?

Accompany your husband when he goes to see his mother.

Have you told your husband what she does when he isn’t there? Does he expect you to visit her on your own?