I saw my friend's crush with another girl

My friend has had a crush on a guy for like 2 years now and talks about him NON STOP. The other day I saw him talking to another girl. They were sitting very close, very intimate. I know that my friend and this boy aren't in a relationship so he's not cheating but If I tell her she would get upset. The only reason I feel like I should tell her is because something similar happened to another friend and she said that If it happened to her she wanted me to tell her first. Do I tell my friend?????? sorry for the complicated text :/