i hate you.
see how simple that was??? now just say it to her but more in the terms of: "look, i know what you are trying to do and i would much rather just stay friends who don't go out together. when you mix in going out then everything gets all confusing and i just don't want that right now."
whatever you do... don't mention that theres another woman... some men try to use that excuse to get rid of a girl, but girls take it as a personal challenge... so stay away from that one
and i've only ever been turned down once... and he was married so