I like a girl but I think she hates me. I am not sure, but what should I do? She goes away when I come sit with her and her friends. She only smiles at me rarely. I am getting suicidal tendencies.

Chances are she doesn't or at least the same way you feel about her. We cannot make someone else feel about us the same way we do about them and its sucks to be in a one sided relationship. Watch her actions and trust your gut more than your heart as the heart has been known to and does lie.  Watch how she acts when you both are around friends as action really does speak much louder than any words ever could. Sorry and good luck