Red flag in boyfriend?

So, I need advice. My boyfriend (of 5 months) invited me to his home last night. He invited me , some guy friends, and his female friend.

She is nice, but I will admit I do feel uncertain if she is "just a friend" or not.

I'm not jealous usually, I've known about her since the beginning of our relationship. She seemed to be friendly, but she is going through a divorce and last night was very drunk/ h! gh.

The problem is that she was being flirtatious in my opinion, like moaning when singing songs, she kept talking about how she's single now and lonely, and even danced to a song with my boyfriend.

Tbh, it seems like they get along better than me and my boyfriend do at times. I'm just genuinely wondering if guys can have female friends or if I'm just waiting to discover they have been sleeping together. Maybe I already know the answer and don't want to admit it, or I'm crazy. . . What do you think?
Red flag in boyfriend?
Add Opinion