<human>: So we have been together for 7 years. Have met our old friends, made new friends of course, and basically we both have the same group of friends that we hang out with all the time. My SO has had a female friend that he considers his best friend and I've been ok with that since she barely comes around. The thing is I have never met her once in all this time that I've been with him. The most recent things that have happened are:

1. She has hung out with him at least twice in the past six months going to clubs or bars at night when I didn't feel like going.

2. They chat all the time on snapchat. (Apparently she is his best friend on snapchat as well)

3. I am currently 7m pregnant and really don't feel like going out to bars obviously, so he invites her to go instead of me. 

4. She has called him (that I know of only once) on the middle of the nights drunk out her mind speaking non sense

Now I know there's no obvious cheating going on but I feel that something is off. She seems like a nice person to get to know. She boasts about being a promiscuous person or that guys are always trying to get with her on Facebook.  Which I couldn't care less about, but knowing my SO is her best friend is kind of suspicious to me.

Can you provide a brief overview of the text?
<bot>: Boyfriend of 7 years has flirty female friend I've never met with and seems to be only interested in hanging out with him.What should I do? Should I confront her or him? Is this really worth being upset about?