Song about liking someone thats taken by some creep and wanting them to realize you'd treat them better?

I like a girl thats in a relationship, but isn't happy.
For certain circumstances, we cant be together.. so its kinda like
forbidden love too.
But I know she likes me too.

I need a song about liking someone that is taken when you know they
like you back?

Any genre.

Thanks! :)

I already have
Trey Songz - Can't Help But Wait
Mario - Let Me Love You
Taylor Swift - You Belong With Me
Taylor Swift - Tear Drops on My Gutair