Most Helpful Girl
Here's a shocker: people aren't romantically interested in everybody.
The girl who wants the guy who isn't interested in her needs to get over it and move on.
The guy who wants the girl who isn't interested in him needs to get over it and move on.
It's just a part of life that you are going to want to be with someone who doesn't want to be with you. The sooner you accept it and move on, the sooner you can find someone awesome who does want to be with you.
Most Helpful Guy
The guy must be very hot for this to happen and the girls will interpret his lack of interest as confidence. A lot of girls don't really know how to court a guy, can't fathom rejection and are more clueless, creepy and desperate about it than the worst 16-year old "nice guy".