I don't want my girlfriend to hang out with my friends
Why don't you want her hanging out with them?
My friends think she is weird.
I'm sorry your friends feel that way.  I think it's good of you to want to keep her from finding that out by keeping her away from your friends.
It's not like they are a bad people. I just think that if they hang with her, I will lose them.
Well if they can't respect her do you think you need to be friends with them? I am glad you are trying to protect her but real friends should be accepting of your GF.