Don't you just hate it when some "Dudley Do-Right Dude" interferes with a perfectly good catfight?

My personal policy on this is,
if she gets herself into a catfight, it's up to her to get herself out of it, regardless of who started it.
The only exceptions wherein I would interfere and stop the fight would be if she was severely injured, like a broken arm or some such, or if I believed that her life was in danger like having her head held underwater or something like that.
You also need to consider the legal liability that you, as a man, face when you inject yourself into a fight between two women. Putting your hands on someone is "assault." If the "Dudley Do-Right Dude" calls 911 and the police arrive while you're restraining that female, who do you think is going to jail? Men are usually considered guilty until proven innocent in these situations, and good luck proving your innocence. That female will tell the police that you and your girlfriend both attacked her.
Also, I will defend my girlfriend if she did NOT want to fight the other girl in the first place, but that was not the question here. If she gets into a fight and gets her ass kicked, that's just how the cookie crumbles. I'll take her home and clean her up afterwards.
Just my personal policy...