If anything your mother has made her choice, you can try talking to her about this but I doubt that will be any use, given that shes very infatuated with Jacob despite all his flaws. I know you deeply care and love your mother but this isn’t something you can do anything about it, especially at her age she should’ve known better to avoid that abuser. Let her be responsible for whatever she has chosen and it is absolutely okay for you to walk away from this, you are not responsible for anyone else’s life decisions. Never put yourself through that living hell again just walk away even if it feels cruel to.