Skarletstarlet,
I'm sorry you are having to go through this again. I know it had to be hard the first time with your EX. But know to go through with it with you mom. While I know you love your mom. We all love our own mom. You have to do what is best for your life. What makes you happy. What brings joy to your heart. Your mom talking bad things about your boyfriend is not. Your mom needs help and until she gets help will lash out. This is the alcohol talking to you. It see's you and your boyfriend as stable and possible you moving out of her life. So it tries to be mean to him to make him break up. Cause if she is mean to you, it might just drive you closer to him and not her.
I hope you can convince your mom that she needs help. I would tell her that you love her, but i need to step away for a while why you get help. This talking mean to me and everybody in my life is bad for my mentality. I need to look after myself and my kids. I know that would be a hard thing to say. I know it would be for me to say to my mom. but your mom has no right to treat you like this.
Just be strong and keep posting and reading here. we are here to help.