<human>: EDIT: Changing the flair doesn't work on my computer. It should be "Relationships". 

I discovered this yesterday when I noticed that the name of an ex-boyfriend was high on the list of Facebook contacts, as if she'd recently talked to him. We were watching something together on her laptop and she went to the toilet, leaving her Facebook logged in. 

A gut feeling prompted me to click on his name, the chat window popped up and there it was. Fairly explicit conversations about sex, him telling her to come visit and fuck him in his new bed, etc etc. I had about two minutes to look through it and I was able to establish this started about three days ago. Not wanting to read any more of it, I closed the window. I elected not to confront her about it right then and there, pretended everything was alright and had an (admittedly) nice evening with her that night when we went out to meet some of my friends.

Do I confront her about this? As far as I could tell, the conversation between her and her ex had tapered off yesterday and when he asked if she wanted to see him, she didn't give a definitive answer. I feel pretty fucking bad about it, but the fact that he lives abroad and they hadn't talked in months before that makes me question what to do, or how serious this is.

Can you succinctly summarize the text in 1-3 sentences?
<bot>: GF started sexting with ex-BF who lives abroad three days ago, I discovered it last night; wat do?