I'm going to ask my friend not to bring his gf to social gatherings
I hope that's not true, why don't you want them to go?
I can't stand interacting with her.
You need to be more tolerant of who your friend decides to have as his girlfriend. Since this is your friend, you should be more understanding of who he likes or your friends will not want to be around you.
Ok so I don't like her and I don't want to interact with her.
Yeah, I believe that would just be the better choice, to not engage with her. It's best to just let your friend do what he wants since it's his life. How would he feel if he were pressured into choosing is friend or girlfriend?