<human>: Hi! 

Throwaway, but I was out at a nightclub on Friday night and I had seen this person, a ginger boy and a girl with long black hair, my friend resembled her, and I almost mistook the girl for her and went to walk over and say hello, but I took a detour when I seen that it wasn't her. We'll call my friend Valerie, and I spoke to my friends who I was out with and said "I wonder if they're friends, can you keep an eye on him?" Which they did, when I went to the toilet I came back and my friends(2 of them) had told me that boy had gotten physical with the other girl and was touching her bum etc, and then surely enough I had seen him do it as well, I have met the boy once before, and he didn't seem to recognize me.

I looked at his twitter to see if it was him or not, and it was, I asked my two friends to confirm it because I was a little tipsy and they weren't. But they said it was definitely him and I looked at it sober and it was certainly him.

I'm just wondering do I tell her? It sounds minor.. But if I was Valerie, I would like to know something like that! He's cheated on her before, and my intentions are to tell her about this, I'm just wondering if I'm doing the right thing?

Can you condense the text into three sentences or less?
<bot>: Saw my work friend's boyfriend flirt/touch another girls bum whilst I was out, two of my friends confirmed that it definitely happened.