I need advice…

So my bf has some female friends, and I don’t have a problem with it (met one of them) but with one of them that he has. Before we got together, him, her, and another guy friend had a trip to Colorado planned. Throughout the relationship, I’ve had an inkling or feeling that something either happened between them, is happening, or he’s emotionally involved with her. Her name is Bri and her name in his phone was “brisket,” as he said that’s what they called her in college as a nickname. I was on IG one night scrolling on her page, and accidentally click on her story. She seen me in her views, and called him asking if everything is okay in our relationship, and asking if I had a problem with her. He brought it up to me, and I denied and he kept asking if I was sure since she sent him screenshots and a screen recording of my view. Is there something going on with them?