It was a party at a mutual friend’s house, there were about 10 people there. We had a good time, drank alcohol and sat next to each other all the time.
At some point two more people showed up – one guy I knew a little, the other I saw for the first time. Let’s call him Matt. They greeted everyone present by hugging each other (Matt and my then-girlfriend hugged a little longer, which surprised me a bit, since they were also seeing each other for the first time).
We went back to drinking and talking. Loud music was playing in the background, some people tried their hand at karaoke, others went out for a cigarette. A typical party.
At one point I had to go to the bathroom, so I left my girlfriend with everyone present. I was gone for about 10 minutes. When I returned the sight I saw made me feel very uncomfortable.
My former girlfriend had her head laid on Matt’s lap who was playing with her hair and stroking her face with his hand.