I'm the mother of an addict but felt compelled to reply because this sounds so similar to the situation with my son. It was hell for both of us whenever he moved home, I was an enabling, frightened codie who watched his every move and took every relapse personally and he had difficulty living within my rules and we quarreled often.
If your mother hasn't already tried Alanon or Naranon or CoDA, maybe encourage her to give it a try. I promise it will help her deal with her fear and her own behaviour.
The decision whether to stay or leave remains between your mother and yourself, but personally I would never put myself in the position of having a front row seat ever again.
Hugs