Dear Mr. Olie,
Your friend needs to find a way to convince this girl that he is better than the wimpy dude. Women are very superficial and care about silly things like a persons ability to beat up other persons. If your friend were to stalk the couple while they are out in a public place together, then proceed to beat up the wimpy dude, he is sure to make a very big impression on this girl. Once she sees him brused, beaten, and crying in public, the "sex-having" with the wimpy dude will most likely lose its satisfaction. At this point all your friend has to do is sit back and watch, sooner or later, after some frustrating anti-climactic physical encounter with the wimpy dude, she is sure to show up at your at your friend's front door and subsequently find her way into his bedroom. Best of luck to your friend on his conquest.
hot.like.C3PX