My mom and dad have moved into our house as they are both mid 80s with numerous health problems. Mom has heart failure and copd, hearing loss and I believe some type of dementia (although she has 2 memory tests at the doctors and they think it’s possibly her conditions). As I say they are living with us and it’s proving difficult. We barely go 2 days without her starting an argument with me, my husband or my dad. She pushes all our buttons until we retaliate then plays one off us against the others. After that we have a period when she acts like she’s unwell and shows signs of confusion so we then get concerned in case she requires medical help. I try to include her in everything and started off by asking her to keep to her own routine but everything tired her out so my husband and I take care of everything now but it seems that’s wrong as I’m not doing things the correct way. I am trying to keep the peace but it’s proving difficult
Tell her you do not like what she is doing and if it continues you will have to ask them to move to Assisted Living. You can not "place" them there if they are decisional. You can however tell them that they will have to find another place to live. An apartment, Condo, house or Assisted Living would all be options they could choose from.
Your other option if it is possible in your house is to divide what might be called an "In-Law Suite" that could be locked off from the rest of the house. This way she would be less able to "push your buttons" 24/7. If they need help a hired caregiver would be an option. (paid for by them)
Chances are you are not going to get her to change so a change of living arrangement might be the only way.
It's probably time to be looking into a nice assisted living facility for them both, where they will be around other folks their age and they can have their own space, to do things the way they want. They will have their peace and you and your husband will have yours. Something to really consider, as your parents could live for another 15 years or so. Are you willing to live like you are for that many more years? Wishing you peace in whatever decisions you make.