Girls, How do I get my best friend and boyfriend to become friends again?

We used to all chill and laugh together. But, against my advice, he sent her an unsolicited pic of himself and a couple of his buddies naked at the lake. She made a joking comment about how cold the water must've been and he immediately just started losing his temper with her. Then she stupidly dug out an old pic she had kept of my exes penis and now he won't speak to her and wants me to stop being friends too
Girls, How do I get my best friend and boyfriend to become friends again?
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