Help?

OK so its this boy I used to like and I guess he talks to this other girl and she doesn't really like him she's playing him. She just was talking to him to waste time and now since her bf( who she been dating for 3 years) and her got back together she doesn't want him. I want to tell him but I don't want to start nothing and since I used to like him I don't want him to think I was just trying to get them to stop talking because I liked him so should I tell him? P.s ik all this because my cousin got in an argument with the girl today and the girl said she don't even want him and she was on sc posting her first love on there with the caption "mine mine mines!!"