My girlfriend has a male best friend and it's hard for me to get over that. Any tips?

I trust my girlfriend first off. And I think I need to get use to a girl with a guy as a friend. Also she has multiple close friends mostly girls he's the only straight guy. Also she did have a point they've been friends for years and nothings happened. But what if he's waiting for his opportunity.. I don't know maybe its all in my head. Also he always calls her late at night. She said thats the only time he's free but still.. no they've never had sex or anything
My girlfriend has a male best friend and it's hard for me to get over that. Any tips?
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