Dude. Don't.
For one thing, she ain't legal. It ain't worth getting in trouble and possibly having to pack soap on a rope just to get some sex. Turn on the charm, and hit something a little older.
Two, it's kinda wrong to do your cousin. Think of any potential offspring you might have, accidental or no. Inbreeding raises rates of genetic defects in children.
At the very least, wait until she's 16, or whatever legal is where you are, and have another think over.