<human>: I met her thru my best-friend, started hanging out as a group with other friends we share and eventually one thing led to another and now we've been dating for more than a month now. At first I didn't think I would mind their friendship, but just as of recently she sent me a snapchat of her hanging out with my best friend pretty late watching a basketball game. Keep in mind they used to do this before we started dating. And to be honest with myself I didn't like it one bit, and I'm not sure if I'm just overreacting or it's alright for me to react this way and do something about it.

Can you summarize the given text in a few sentences?
<bot>: Gf hangs out with my best-friend, she did this before we started dating. Now that we're dating I don't like it one bit, am I overreacting?