Definition: Given a real-life anecdote of a complex ethical situation, generate a suitable title that describes the main event/root cause of the situation. Imagine that the given text is a social media post, and you have to write the title of the post, so the users can decide to read the main text or not.
Input: Me (20M) and my GF (19F) recently got into an huge argument because I found out she made out with a guy at a party but lied to me about for 5 months. We weren't dating at the time but I asked her if we could exclusively hook up 2 weeks prior and she said yes. Her biggest defense over this is that "we weren't dating at the time of the incidence so what does it matter". My biggest issue about this is the lying for the 5 months and that regardless of the dating we agreed to be exclusive. She says she wouldn't care if the roles were reversed but that argument in my mind is extremely invalid because the roles aren't reversed.

Need some good advice.

P.S. first post on reddit sorry if this isn'y formatted the correct way.

getting mad over my girlfriend doing something before we were dating but I asked her to be exclusive