When Jack was in his relationship with Rachel, people had always said that he was more of the “girl in the relationship” even though he was a guy. After he got hit with the magical lightning bolt, though, he was a girl in more than just his relationship. He got a new job, got a new life, and got some new friends. After one of the guys at his new job asked him out, Jack realized he was still straight, even as a girl. He called Rachel to get her to help prepare him for his first date as a girl. Now, he would be the girl in a new relationship, both literally and physically.
