Is OTHER wrong in the post ? POST : There's a couple I know who are dating and the guy is head over heels for her but she doesn't feel the same. She's cheated on him at least once (in the last 2 months) and flirts with her ex's on a regular basis, as well as reminiscing about the times she spent with her ex saying "look I was actually happy then". She constantly posts pictures of her and her ex on her private story. 

I think it would be better for him long run but at the same time he seems to be very happy with her.

So WIBTA if I let him know what's been going on?