Build a Friendship, or Go For It?

I've liked this girl at school for a year now, but am not really good friends with her. Recently, she ended her relationship (prefering not to take it long distance), and I had just broken up with my girlfriend earlier that same week. I do not know if now is a good time to start showing interest, as the "break-up wounds" might still be wide open and she's just not showing any signs. Plus, I don't want to be too friendly and end up in that friendship zone. The school dance is coming up, but I don't want to seem as though I am rushing or desperate to take her. Her friends say she likes spontaneousness, but is this just reckless?

Take it slow, but DON'T "build a friendship". Make it clear from the get-go that you're interested in her romantically. If you build a friendship, you'll screw yourself... once you get in the friend-zone, she'll never think of you that way.