I think this girl is flirting with my boyfriend in front of me. It's kind of annoying me.
How do you think he's reacting to it?
I think he is having a lot of fun with her.
If you're annoyed at the situation I understand why that would be the case. You expect your boyfriend to be loyal to you which is normal but this girl is openly flirting with him and he isn't dismissing her. Don't get too upset though and just talk to him about it later.
I told him and he got all mad at me because I didn't trust him. He told me that nothing is going on.
That sucks. He should have been more understanding about it but if he says there is nothing going on then there isn't much you can do but trust him.