A chick named Amber

So my boyfriend has this friend amber that he just recently told me about. The only reason he told me was because we were laying in bed and she messaged him. I know I shouldn't get mad cause it's an old friend but they met on meet me. And they only hangout alone, she's single and he was saying how much she just loved hanging out with him. I don't know what's happening with them and I can only rely on him telling the truth because they only hangout alone. Any suggestions on how to figure this out?