<human>: Can you condense the text into a few key points?

Ok, I'm 20, she's 19. We've been dating for just over 2 years. She lives in a dorm but spends a lot of her free time at my apartment.
Here's the story: Today, while I was at work, she went over to my friends' apartment (4 guys, 3 single [my friends, not really hers]) and slept. Then, she went out to eat with a couple of them and one of their girlfriend's (the not single guy). We text all the time while I'm at work and she's at home, but she failed to mention any of this while I was at work. Tonight, whilst I was playing with her, she mentioned it passively like it was no big deal. I was really bothered by this so I asked her to leave. "My dorm has no heat, what do you expect me to do?", I reply with "Not my problem, please leave". Long story short and a little calm back and forth, she left. Now she's talking about breaking up and blah blah blah she does this every time we fight. She kept asking me why I can't talk to her about this... "You never want to talk!", etc. I told her, "You told me what happened, I asked you to leave for a night so I can get over this. I know what happened; There's nothing else to talk about". Am I in the wrong for kicking her out? I don't really suspect cheating but I want to set the precedence that sleeping at my friends' apt is not alright. Also, sleeping at my friends' and not telling me, is really not alright! I tried to condense this as much as possible so I will answer any questions asked. Any help would truly be appreciated. Thanks
<bot>: My girlfriend slept at my friends' apartment while I was at work and didn't tell me until 6 hours later. I kicked her out for the night. Was that the right thing to do?