You do not have to feel bad at all!!!!! I JUST realized this with my father. He is an alcoholic, on his third marriage (of which they both got into cheating on their significant others). He has basically abandoned all of us for her.

I have always let him claim me on taxes even though I moved out before I graduated high school. Finally I said "no!" "I'm the one paying the taxes and I'm the one getting MY money back!". It took several years though because I felt bad for their financial situation. But, I had to remind myself that he put himself there. He is the one that buys at least a 12 pack or a case a day. He's the one that cheated on my step-mom and ended up in jail for trying to strangle her. He is the one that put himself in this situation.

So even though it hurts so bad to watch your mother do this to herself, that's exactly what's happening - she's doing it to herself. What you are doing is enabling. One more person to do something that (to her) is justified simply because she gave birth to you. You do not owe her anything if she can't help herself. I hate to sound so harsh but save yourself. This is a cycle that will only hurt you if you stay involved in it.