Why would a girl go after a guy that with low self-esteem, no confidence, and no physical attraction?
The reason you like this movie is because it is a fantasy, as in You want it to be realistic fiction but it's just Fiction... Like Scientology.
There was no reason for those two to be paired up in a movie; Alice Eve is way too pretty for that part, and Jay is extremely nerdy, which is why he was cast. The sexy frien of Alice is way too pessimistic, but still makes up for it in the end with her comments that lead Jay to chase after Alice.
Footlong was the best actor in the movie.