Be the ass she knows ( and loves )
Gift her with this fancy little jewelry box that contains not an actual ring, but a tiny rump ... that FRRRRTS (sound effect) when opened. This may be more appropriate at the end of the relationship. Results may vary. It comes inside of a nice little gift box - ready to rip. This could also be useful in making a smart and final "Kiss My Ass!" statement. In any case, you will make an impression.