Am I overthinking? What are your thoughts?

My best girl friend created a group chat with her, my boyfriend, and her two other friends that are not mutual to my boyfriend and I. I am not included in that group chat. My girl friend told me when she first created the group chat it was to help “prove a point” or win an argument between her and her friends. Now they just talk all the time.

My girl friend tells my boyfriend drama/things that she doesn’t tell me. I know this because when my boyfriend and I are together and he is texting her back I get a glimpse of their conversation.

I wonder why I am not included in the group chat in the first place or why she doesn’t tell me things that she tell my boyfriend. My boyfriend and I both don’t really know her two other friends but we do know she exists because my girl friend talks about her. Please keep in mind that my boyfriend met/befriended my girl friend through me because I went to the same high school with my girl friend.

I’m really trying to be understanding and not overthink, but why do I feel so weird/uncomfortable about it?