Would you be mad?

My boyfriend is working on a project with a girl, he said the first day he met her she told she has a tribal feather tattoo on her bum and she flashed him to show him it. Well, today he had to work with her on this project, & he told me that she started telling him she loves to drink.. So he goes over to the fridge and he says they had one shot.. They were alone in his room this whole time & he called me 30 mins after she left to tell me this. I told him it kind of upset me because this girl had flashed him & wanted to drink with him, but he says I'm being silly for getting mad over a "Friend" would you be mad? Or am I just being an overly jealous girlfriend?