Your mother may well have felt helpless because of both your father and you. But like so many other feelings, we can't make anyone feel anything. Your mom may have felt helpless because your grades were failing and she didn't know what to do. Does that make you a bad daughter? No, that makes you a normal daughter.

It can be easy to fall into the trap of "it's all my fault". But it's not. Your grades were just one small factor in a whole lot of messed up stuff between your parents. Your kid selves may cling on to the self blame because it's somehow easier to digest than saying "I was screwed over in life, and it's not fair, and it hurts and it sucks".

When I read what you T said, it sounds to me as if she's talking about your mom's helplessness over your dad's alcoholism. And even if your mom did feel helpless about you, that says more about her than it does about you.