Not sure what to do

F47. Dad is 78. Stepmom is 74. Stepmom is diagnosed borderline, but doesn’t go to therapy because she “tried” and “therapists always blame her for things.”

Dad remarried five years ago. Initially she was lovely, so happy for him to have a companion who cared for him.

Cracks started. She is impulsive in spending, my dad is the fourth husband and sixth engagement, prone to jealousy, entitled, wants everything her way. My dad has cashed out over 100k of his retirement, sold his antiques, his truck, and his tractor. He was happy to pay for her, says she was “down on her luck” when he met her. She was sending money to her daughters, both of which are often in and out of jail for substance issues. NONE of this qualifies me intervening - my dad has a right to spend his money how he likes on who he likes, he is a grown adult.

He was recently hospitalized for septic shock. Her verbal abuse/gaslighting/manipulation of my father escalated. She went ahead with her third facelift since she married him while he was in the icu. She then left him to go out of state while he was in rehab for ten days because “she needed a break.”

My dad was hurt. And stressed. And HOSPITALIZED. When she came back, he tried to address how hurt he was based on her actions. she told him he was petty, short, and self centered. She told him he was just jealous of her because she had a good time and she’s an angel who is the perfect wife.

At this point I intervened and she went full split on me. She’s split on me before, belittling me or saying something gaslight-y, but not like this. She called me a disrespectful brat, disgusting pig and that I should go “off the planet” just like my mother did (I’m not sure if Reddit will let me post what she actually said - but I think you can read between the lines). Amongst other things. She took no responsibility for the hurt she caused my father - just kept saying she didn’t do anything wrong. I grey rocked her the entire conversation (super proud of that).

She is now escalating and telling my father he is to choose between me and her. That she will leave him if he tries to visit me (I am out of state).

I’ve told my dad I love him and my door is always open. I’ve told him I think this is a toxic manipulation to try and control him. All he says back is that he wants us to be a family. I tell him I’ll always care about him, I’ll never make him choose. He says me maintaining my no contact boundary with stepmom IS making him choose. It’s her words coming out of his mouth.

I’m at a loss as to what to do here. Seems they are enmeshed for different reasons, with her borderline. I’ve tried to be empathetic, but going after my mother was a line that I don’t think I can come back from. I’m literally losing my father and he’s still alive. Any advice appreciated.