I'm not going to invite my best friend's boyfriend to see her graduate basic training
Why don't you want him there?
I'll explain simply: I don't like him and I think he and I wouldn't get along.
You don't have to like him. But it's not up to you, it's her graduation and she gets to decide.
That's fine. I think it's weird that to invite someone to another person's event.
It wouldn't be weird to invite them since they would want to be there. And it would be rude to not want them to be there for their partner's special day.