My girlfriend started working with and talking about this girl, and inviting the girl and her GF to go to dinner with us. We went on a double date with this couple a few times over the course of 3 weeks, and I noticed every time we were all 4 out, my girlfriend would drink much more heavily than usual. We were having them over for dinner one Sunday but had an adult sports game before (which usually involved light drinking) and she was acting super weird about making sure we were home on time and had dinner ready, etc.

That night, after they left, she passed out on the couch next to me. Her Apple watch buzzed, and I glanced over and saw a selfie of this girl. Which was enough to get me to look at her phone (for the first time ever), where I find texts with sexting and details about their hookup. I took screenshots of all of it and sent it to my phone.

I got dressed, texted a friend, packed a backpack, and woke her up by throwing her phone (with those messages open) at her and walking out the door. She groggily sorted it all out and attempted to contact me all night and eventually texted the other girl's GF those screenshots, which I thought was pretty sh*tty. Sort of an 'if I'm going down, you're going down with me.