How do I invite a friend to my engagement party and wedding, but not his girlfriend

I have a friend I’ve known for close to 15 years now, who I absolutely love. He’s a close friend of mine and my fiancé’s… the only problem is we can’t stand his girlfriend. No one in our friend group likes her as a matter of fact. They’ve been dating for a couple of years, and live together, so I consider them serious. I really want him to come to my engagement party (and eventually my wedding) but I absolutely cannot stand this girl. She’s very opinionated (her opinions are often wrong and not based on fact) and argumentative if anyone disagrees with her. She’s insulted mine and another close friends professions. And is all around annoying. I don’t want to chance ruining a friendship by either not inviting him to either event, or saying he can come, but she can’t. And I also don’t want to invite them both, because I don’t want someone there that I don’t like. Is there a tactful way to confront this? I’m not very confrontational and try to please my friends best I can usually. Has anyone been in this position before? What do?

Edit. It will be a very small wedding 25-30 people.