My girlfriend jealous of my female friends?

So i am working in a company where i have mixed friends , we travel together and stuff , my girlfriend now is not letting me meet my female friend for no reason, my female friends knows about her, they even picked with me her birthday's gift, i tried to explain to her, but she said there is no friendship between a boy and a girl.

what to do please,

My girlfriend jealous of my female friends?
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