Will cheating on my girlfriend get her to lose weight?

I don't like the pounds she's put on since we had a child last year. I don't like the way she looks. I bought her a treadmill for Christmas (she didn't ask for one...ooops!) and she won't use it. I send her nasty text messages from my friends phones calling her "fat ***" "cow" etc. hoping to shame her into losing weight. It doesn't budge her. I've cheated on her now 3 times with 3 different women. I am planning on telling her tonight that I've cheated on her because I don't like how fat she got and I'm going to continue to do so until she loses 15lbs. I don't know what else to do. Would this work for you ladies out there (or you have any other suggestions)?