My Boyfriend let another girl borrow his jacket in front of me?

Its pretty cold where I am right now (we get weird weather all the time) and I am working on this film project with my boyfriend. Well, the other day we were filming outside and it was about 31’ F (I told you it was cold). Anyway, we were standing around while the crew was getting the next scene set up when my boyfriend saw one of the actresses shivering. Now, this girl has been flirting with my boyfriend since the day they met, so I wasn’t comfortable with them talking to begin with. Anyway, he asked if she was cold, and she said she was freezing. I went over to them just so they weren’t alone, and hinted that I was cold too. But then, he takes off his jacket and gives it to the other girl. Right in front of me! Granted, I was wearing more clothes than she was, but only like one other jacket. What should I do here? Should I talk to him about it? I’m kind of scared to approach the subject. Any ideas on how I should if I should? Thanks.

Btw, its been like two days, and she hasn't given him the jacket back. And he's fine with it. He keeps saying, "if she still needs it, let her keep it"