<human>: I've never met this guy (living in a different state), but I was bored and added some people via snapchat-- on a reddit post that was clean and friendly snapchatters only, so i could just have more stories to look at when I am bored and talk to new people.

I always ask about the person and what they do, if are they single etc so I dont cross any lines if we are both mutually interested.
One guy in particular started sending me provocative pictures -- I didn't want to send anything fully exposed of myself back and he was okay with this. He has been sending me pictures/videos and messages for at least 2 months now.

Flashforward to today: I decided to do some stalking on instagram after knowing about him and assuming he used the same username on both accounts (he did) .... and i've just found out he is in a 1+ year relationship.... Should I contact the girlfriend? or just leave it? would you want to know if your partner is sexting other women? Not sure if its my place to tell, so I'm not too sure about my decisions.

Give me a shortened version of the text
<bot>: sexting a guy, who I just found out has a girlfriend, should I tell her? would you want to know?