Hi jen29,
Tough place to be in. Sorry your in that spot.
Sounds like your mom is manipulating the situation by turning the tables on you and making
you feel guilty for her wrongdoings.
It makes sense if you think about how abusers etc spend years trying to justify their behavior. It's the denial and blame game.
Maybe you should just tell her straight out that you understand she feels bad so "you can only imagine how bad I feel."