I do not own Harry Potter. JKR does.
Hermione Granger could not allow herself to fall for Ron Weasley's older brother, even if Fred paid more attention to her. He was only a devilishly handsome ginger who ran a successful and profitable business with his other devilishly handsome ginger twin.
Hermione Granger will not admit that Fred is ingenious. The portable swamp? All those beautiful and sparkling fireworks? Perhaps he is incredibly creative and talented, even if he did have a certain disregard for the rules and a carefree personality.
Hermione Granger does not have a crush on Fred Weasley. He was just humorous, outgoing, charming, sarcastic...and perfect.