<human>: Give me the gist of the text in a nutshell

The background is that ever since my friend has turned 21 she and I have been wanting to go to the bar together. We are really good friends and this alone makes my girlfriend jealous and uneasy. 

The problem is that to go out with my 21 friend I would have to leave my girlfriend behind. She doesn't have a problem if I go out with my friends who are 21 and male, but every time I hint at wanting to go out with 21F we get in a fight about it. 

My girlfriend has always been very jealous of other girls that are my friends and it bother me that she is so jealous of them that I cant even hang out with my friends without getting in a fight with her. 

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<bot>: )Is it wrong of me to go out with my friend who is a female, even though we are just friends. Or is my girlfriend just very jealous.