What happens, IN HER MIND, is that she comes to see you as WORTHLESS simply because she hasn't had to INVEST anything in you in order to get you or to keep you.
You were an interesting diversion while she had nothing else to do. But now that someone a little more valuable has come along, someone who expects her to treat him very well, she'll have no problem at all dropping you or demoting you to lowly "friendship" status.
Quote taken from The SoSuave Guide to Women and Dating, which you can read for FREE.