Have you ever thought you had an understanding with someone, and they just turned around and proved you wrong?

Oh how annoying! I would just keep trying to explain it to her. Luckily, I'm a very patient person and don't find this too difficult. You might, however, try telling her that you've quit and that you haven't got any. Then she'll have to buy a pack of her own and you can go and bum off her lol! :P