Is it normal or am i being selfish?

My Aunt and Uncle are having marital problems and my Aunt is constantly complaining to me about her husband and her depression (which go hand in hand). I am 20 years old and my Aunt is 47 and she has been doing this from the time I was 18. I really feel that she needs to take responsibility for her depression and marriage and quit laying her problems on me because I do not have nearly the life experience to properly interpret what she is saying...

I'm serious. She constantly gives me the business about her depression and her marriage and I know that she is just venting, but she claims that she wants help and she says that because of her depression, she has no motivation to get help. I WANT to help her and I have TRIED, but really it just ends with me doing all of her housework for her as she sits on her can and complains some more.

I have really done everything I could have thought of doing, and I am very bitter that she (willingly or not) put me in the situation in which I am presented with this hopeless situation and I can do nothing to mend it, no matter how hard I try. My family has this way of doing this to me (my parents did the same when they got divorced and I was the "pawn" so to speak), and I am so fed up with it that I do not even like entering that house. It makes me so miserable to hear that she is so miserable but I can do nothing to help and she won't help herself. I want to remove myself from this seemingly toxic situation...

Are my feelings normal, or am I being selfish and I need to keep being the proverbial "shoulder to cry on"...
Is it appropriate for a middle-aged adult to lay these issues on me?