I want to remain friends with a female friend that my gf does not trust
Why do you want to be friends with that girl?
Because she's a very nice person. My girl friend can sometimes be overly-sensitive
I hear you, but it is problematic to hang out with someone your life partner does not trust. You should really talk to your girlfriend about it and see if she can get to know that girl better. Otherwise you might be getting into a world of trouble.
I guess I don't understand girl stuff
It's okay to be confused. You are just a person who doesn't get jealous of things like this.