Most Helpful Guy
Absolutely! Emotions and feelings are not easily understood. As long as the girl doesn't ignore the guy and is just super mad at him for not having feelings for her right then and you stay his friend, then feelings can definitely develop. It might not happen, but it is absolutely possible
Most Helpful Girl
unlikely, but it is possible.
If he rejected her he obviously wasn't attracted to her or has his reasons.. so something would have to change his mind.