What's the rush? you're 13. just enjoy hanging out with her without having to deal with the nagging, paranoia, wasting money on stuff she'll eventually throw away. Need I say more?
If you insist on pursuing her, just ask her out. The worst she can say is no.
Actually the worst she could do is kill you, but that'd be a little extreme.
Also, I can't believe we've made it 15 posts without saying "stick it in her pooper."
My advice is stick it in her pooper.