I'm going to ask my fiance to have his daughter leave our house this weekend
What is wrong with her?
I can't stand her, she whines too much
You want to try your best to get along with your partner's kids. All children whine, and if that is something you cannot handle then maybe you and your partner are not going to work out.
Maybe you're right.
You should try your hardest to keep the peace. Kids need their parents and I get it can be really hard and frustrating to be an outsider on that relationship.