Not your circus, not your monkeys. Simply because someone had sex and you were the byproduct doesn't mean they were ever good for you in any way or that you owe them anything. Many people have toxic and abusive parents that end up spending their lives acting like they have Stockholm Syndrome, chasing that love from people that never had it for them, continuing the abusive cycle. I'd walk away and leave her be. You're likely going to drag your heart through the briars again and for what.
I find that many ex-JWs make a mistake of seeing their parents through an ideal lens of who they wish they were instead of who they actually are. They spend their entire lives never being good enough for people that are often abusive and possibly full blown narcissists. You can't get anything good and they will take everything they can from you, leaving you broken, just the same pattern as the cult but in the form of a parent.
You gotta know when to hold em, know when to fold em, know when to walk away, know when to run. Work on grieving that bad relationship and accepting that it is what it is and losing the tight grip on a hope that it somehow could be different, and let it go.
If there's some sort of elder abuse you could report then you might do that but then it's out of your hands. And just because your abusive mom requests you doesn't mean you have to indulge her.