Okay, so you’re 26 and he’s 28 and there’s a four year old child who’s either one of yours or yours together. He’s got an ex who he ditches you for now and then, and who is rude to you. You are not alone! This is very common and the way you handle this is important. Remember that this is between you and your boyfriend — not the other woman. So be polite to her and stay cool. Don’t put her in the middle of your relationship. The more you make her relevant, the more relevant she’ll be. So just stay cool and focus on your relationship with your fiancee.
Next, understand that you have competition. That’s not a bad thing, but you do have to rise to the occasion and bring your A game to the relationship. Be the best girlfriend or fiancee you know how to be. Make him grateful to have you and not want to lose you. Remember that men don’t cheat because someone else is fabulous — they cheat because they feel something with the other person that they don’t feel in their relationship with a partner. So put the focus on your relationship — not on the distraction in it.
Ideally, your fiancee will realize what he has in you and let her fade into the background. It’s important you don’t create a mountain out of a molehill — she may not be the horror show you think she is, and instead, may be more of a nuisance than anything else. But don’t give him an ultimatum or badmouth her — that will just make her more of an issue than she is.
I hope that helps!