Can anyone tell me some good "love anguish" songs?

Preferably sung by a girl...pop, country, rock, etc. Songs where she really likes a guy who is unavailable, not because he's with another girl, but because they're in two different worlds and/or because they just aren't "supposed" to like each other. ALMOST a Romeo and Juliet feel but where the artist doesn't know how the other person feels. Kinda complicated, i know. But if any songs come to anyone's mind, i'd appreciate it. :) Thanks!