nuts. if she's insanely in love with you and you just wanna fuck her, she's going to get deeply hurt when you dump her, and then what?
stay clear of that trouble.
also what porkie says "if both agree" is impossible under the conditions-- she may lie to get you in the sack, but eventually she will demand "love" in return; and then you'll be in trouble, brother, with a stalker, or worse.
oh yes:
http://www.sonicyouth.com/gossip/showthread.php?t=13914