What you do when a girl you know is suffering?

Be more vocal? If all you're doing was listening then try to give her more support through words. Not much else I can suggest.

I hate feeling like that, specially with the girl i love, and i also feel stupid because i'm too scared to tell her how i feel, i feel like if i do, our friendship will be broken and crap ;o;

You might want to think about that. You may already be in the "friend zone" and confessing your love to her with no reciprocation is going to lead to trouble.