There is a rule called the 80/20 rule: the girlfriend has 80% of what the boyfriend would consider a ideal girlfriend but this other girl has the other 20% that the boyfriend would consider a ideal girlfriend.
tell him he will never get the 100% ideal girlfriend and that it is the bond you form with you girlfriend that makes her beautiful.
what you friend is experiencing is mere sexual attraction nothing more. love is made of: sacrifice, understanding, and acceptance that is true love
Sam_Dawg