... if I say "I've got a penis so small you'll burst out laughing when you see it and I couldn't possibly please you" will that get her to bugger off and lose interest?

Need a way to reject her "without rejecting her" because she's absolutely the type to hold a grudge, be annoying (she already is annoying) and possibly tell serious lies about me if I anger her (she already does tell "joke" lies about me)