I'm going to cut my girlfriends only friend off because he flirts with her
She is going to get lonely without any friends
Of course I can understand that, but I'm not going to betray my girlfriend.
I do not think that that is okay. You cannot control every aspect of your girlfriend's life. This comes across as very possessive.
I don't care what you think. I just want to protect my girlfriend.
You are being very controlling. You need to trust your girlfriend and let her live her life.