I have a problem, please help?

So, I'm 15 years old, and I lead a GREAT life. My parents are the best, I'm SOO lucky, I go to a nice school, I have NOTHING to complain about. However, sometimes, I feel like my mom dumps too much on me. Not chores or work or anything, but she talks to me about my dad and the problems she has with him sometimes. I feel like a mother shouldn't say those things about her partner to her children. I don't want to hear about that. That's something she should tell a friend, isn't it? Not me.