After being given dual POA, can my mother call the bank and have my brother removed as her financial POA?

My mother is 80 and has dementia also is narcissistic. When our oldest brother died of drug and alcohol abuse at 60, my mother appointed my second brother to be her dual POA. He has done great job so far and shares with me every transaction he makes helping her with her bills and payments needed for fixing up our families rental. He moved $2000 from her money market account and transferred it over to her checking to pay for roof and AC repairs on the rental property. She has forgotten she signed the check to have these repairs done and now has accused him of stealing her money. He has documented and has kept receipts of the work. She will not accept it when he's explained it and even showed proof. She now has removed him from being her POA of her finances. She's called me and told me he is stealing her dishes, money, etc. I've explained that he moved the money to take care of the problem at the rental and now says to me that I don't believe that and am always taking his side. My second brother and I have become very close over the years because mom was an enabler to our oldest brother and we have always taken a back seat to him. So now we are concerned that she will remove us both from the will (which she holds over our heads at every opportunity). My mother has pulled my hair and dragged me by it back into the house and have said to me on numerous occasions " I could just kill you!" At age 14. My brother the good son has done nothing wrong but her constant accusing of him of stealing her money has actually made him happy now that she has removed him. My question is, when she goes to realize that she needs his help with her finances, should he help her or just let her take responsibility for her actions till the social services come in and has her enter into a assisted living situation? We have home care coming over everyday to make sure she gets bathed, medication, and doctor appointments etc. when she sees the bill from the in home care? She is going to have a fit at the cost and not want them there every day, because it is exspensive! She is very very greedy to me and my brother but was so generous to our oldest now deceased brother. I flew to FL from NV to help her bury him at her begging and she never offered to pay for my air fare or nothing. My bro and I discovered that in the last two years of my brothers life, between 2015-16. $89k was taken out with no paper trail. When we've asked her about the $30k in my deceased brothers account, she said that was his money. I know good and well that someone on SSI is not going to be making $30k in just two years! My mother sold our home we grew up in and that my Daddy built ( bless his heart worked so hard all his life) my good brother and I never received a dime, I bet that's how my deceased brother got $30k. Now she wants us to help her pay for her care. I think it's a blessing that she removed my good brother from being her POA so now she can deal with it herself and maybe realize how good a person/ help he was to her. I told him if she begs him back to help I told him have her lawyer do it all. But that may cause us to be removed from the will because she is a narcissist . Any suggestions?