I didn't know I had a sister!

Kidding, of course. But your problem is not little or unworthy of help. Your mother seems very self-centered and seems to be using emotional and psychological tactics to control those around her. I'm very sorry you have to deal with this.

I am a big advocate of stepping away from a family member if necessary for your health. That's not selfish; it's smart. I hope you can get some physical and emotional distance ASAP. She sounds very damaging.