Vortex, make her go with your brother!
Nora I'm sorry you are dealing with family asshattery.
The worst situation I know of is what happened to G'ma (Mom's mom). So my Mom's parents were married for over 50 years and my grandfather died of lung cancer. G'ma and Grandpa had been good friends with another couple who also was married for 50+ years, and in that case the wife died.
So G'ma and her friend, F became romantically involved and decided to get married. This is after both deceased spouses had been dead for a couple of years. Everyone sane in both families thought this was wonderful. Everyone insane in the family (which would be my Aunt W and F's daughter "Nomi") thought this was horrible and a desecration of the memory of their father/mother!! But G'ma and F had a great marriage until he got sick and died. G'ma and F also had a prenup and the only main thing was F made arrangements so G'ma could continue to live in their house until she was no longer able to, at which point it would go to his heirs.
G'ma, only lived there for about a year until Nomi made things so miserable by dropping by unannounced, getting copies of the key and just walking in, taking stuff and making nasty comments that G'ma moved back into her house, which luckily she hadn't sold.
Nomi also managed to get a bank teller to give her access to G'ma and F's joint account and took money from it; challenged the will in court, and sued her own siblings for a bigger share of her inheritance.
Unfortunately Aunt W is also causing drama now that G'ma has died. Mom's sister J helped ensure that G'ma could stay at her home until it became unsafe for her to stay by herself for a few hours. Because of this there's actually an estate to settle and it wasn't eaten up by nursing home costs. So my uncle suggests - why not give J a bigger share of the inheritance since she's the reason there even is one. W has balked that she's "poor" and can't afford not to get the money. I'm not sure how accurate this is but now J isn't talking to W at all.
Although there is background of tension. My Aunt W is 70 (I think) and according to her own statements, still resents the fact she wasn't an only child. This is based on statements she's made in the past few years. She was also in complete denial about G'ma's dementia and at the end when J and Mom were praying that G'ma would just pass in her sleep W was talkign about how much she just wanted G'ma to "get better" and live longer. At this point G'ma was in extreme pain and had severe dementia. But W wasn't ready to let go so she was hoping G'ma would live longer.