<human>: Can you succinctly summarize the text in 1-3 sentences?

My current girlfriend went to a party and performed oral sex on a guy there. I did not know about it at the time. Her and I were talking about taking our relationship to the next level at this time too.

The next day I asked her to be mine and we became a couple. She told me she kissed him a week later but I forgave her. Fast forward a month and she reveals that she performed oral sex, after I asked her if there is anything else wrong. She is still friends with this guy. I don't know if I should break it off or not.
<bot>: Girlfriend have oral to a guy the day before we became a couple. Lied about it. What do I do?