<human>: Can you condense the text into three sentences or less?

Hi Reddit, sorry for the long post but this has been really troubling. I've been dating this wonderful girl (and fellow redditor to boot) for the past 9 months, and everything has been going great aside from the occasional small fights. 

Last night she had dinner with a male friend of hers that has always had a thing for her (she has repeatedly told me how he wouldn't stop starring at her breasts when they have dinner), where they shared a bottle of wine. After the meal he invited her to go to his apartment so he can teach her how to dance Waltz and **after** the dance lesson proceeded to touch her excessively, even in the thigh area. 

Now between the wine, the "dance lessons" and the touching there are already enough red flags for me to be concerned, but after she left his apartment she texted me "I'm sorry" and "I went to his place". I confirmed right after that she was just trolling me, although I know she's a total troll and we often joke about seeing other people, I was still understandably worried and angry. I wanted her to talk to her "friend" right away and let him know that whatever he was trying to pull on her was unacceptable and that he needs to get the message asap, or else I would do it myself. And now my gf thinks I'm acting totally out of the line and blowing things out of proportions. I have absolute trust in her that nothing happened but I've never met her friend and do not have the same faith in him, so am I just being insecure and and acting unreasonably? Or am I justified in letting the other guy know what he did was NOT ok?
<bot>: Gf went to male friends apartment after a drink for dance lesson and was touched excessively, should I let the other guy know he's crossed the line?