How can I comfort her when she's depressed?

I have strong feelings for a girl at school. We've become good friends, but after knowing her for over a year, I'm starting to see all the problems she has going on in her life. She feels responsible for keeping her dad happy since her parents are separated, even though she's only 15. She gets so much **** for being unique. I think it's very cute when she starts to dance to a good song on her iPod, and her deliberately bad jokes... I feel like she has a happy mask for everyone, but inside she's hurting. I know she takes drinks from her pantry because she feels worthless. I think she's beautiful... but I'm not sure how to handle it. I don't want to freak her out and make her worry about anything else, like me liking her.