(What makes you think I made the mistakes in the relationship!)
Your wish is granted. You're girlfriend is now as hot as me. Unfortunately, since I'm a male, that also makes her a male. Your girlfriend is now your boyfriend.
Fortunately for you though, your relationship is not going to be homosexual. You become a woman and thus the girlfriend. But you end up being a rather homely girl, thus causing your boyfriend to wish the same wish you just did.
This causes a cycle where you and your girlfriend (or boyfriend, I'm confused now) switch genders. Eventually, the process messes up and you both become pregnant hermaphradites (male/female combined).
I wish I never existed.