My mom moved in with my wife and I a couple months back due to triple negative breast cancer and she is driving us insane. She is cynical, pessimistic and difficult to deal with. We have tried to be nice, firm, straightforward but noting works. My wife is fed up. This $hit is hard.
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Does she have enough money to live on her own and hire aids?
If not, you can connect her with social services for her county. Maybe she's a candidate for Medicaid.
Are you her PoA? If so, I hope it's durable. Does she have an Advance Healthcare Directive? She can create a very detailed one with her oncologist.
If money is an object then she'll have to apply for Medicaid.
Even though your mom has cancer your marriage and your wife MUST come first. Period, end of sentence.
Mom must go.
You and your wife can help by laying the groundwork for whatever your MIL's needs might be. Gather brochures from assisted living if that's a possibility. And/or brochures from in-home caregiving agencies. Get information on senior transport services or set her up with the Uber and Lyft apps. Find out about how to sign up for Meals on Wheels if that would help. Whatever will help so that you can't validly be accused of abandoning her (although she may still claim that, but at least you can say that the accusations are false).
Tell her point blank how her moving in is effecting you.
Tell her mom I want to make sure you are safe and have help when you need it so you and I will go look at some Assisted Living apartments. (don't call them a "facility" or a "home" the word apartment has a better feeling to it)
Maybe your mom really just wants to be back in "her" house. I get it. I would probably have a lot of mixed emotions having to move from MY home into someone else's home.
Does mom need help on a daily basis? If so Assisted living would be good
If she needs occasional help is it possible for her to return to her home and have a caregiver come in to help her when she needs it?
As her care needs increase she may either need full time help at home or she may need the constant care that she would get in a Skilled Nursing facility (again do not use the term "nursing home")
So. Imo there needs to be an end in sight for your mom's stay with you. If she's not being treated, she may need to go to Skilled Nursing for 24/7 care and hospice until she passes, Idk the details. But you cannot have her ruin your marriage by staying in your home for the duration.
Best of luck finding another living arrangement for mom.