How can the problem of a young man being attached to a foreign girl be solved, given that they both know they must stay away from each other, and he wishes to convince her of that?

This infatuation is an inevitable consequence of laxity in the beginning. The lovers, who are non-mahram to each other, must repent sincerely to Allah. The conditions for repentance are outlined in Fatwa no. 32521. The cure for infatuation is easy for anyone who possesses strong resolve and a sincere desire to rid themselves of it. The details of this cure are available in Fatwa no. 34504.