Most Helpful Guy
I know girls like this. Guys too for that matter. Major downer.
The thing with these people is that it's usually in their nature. They fish for sympathy, not advice. I bet when you offer advice, it gets butted aside pretty quickly huh?
The other thing with people like this is others tire of them eventually, which may be why it seems the way it is for you. You might be the only person right now that will seem to listen to her.
If you like or love this girl, you should bring it up (diplomatically). Be the rational one. Point out that all you two ever do is talk about her problems, and you want to help her with them, but you also want to do happy sh*t with her too. No one can take too much negativity. That's no way to live.
But all is not lost if you dig this chick. Talk to her calmly about. If she explodes on you, then I can't say you're going to get much happiness out of this one man. It'll just run you down eventually and there's lots of girls out there who spend more time just enjoying who they are with (you).