There would be a more confrontational attitude from most boys when it actually comes to punishment, but girls are more likely to give way at that point, and probably turn on the waterworks or close to it before the punishment is given. That could be genuine remorse or maybe a sham. In that case I would be prepared to give the benefit of the doubt, to both boys and girls. And this would account for lighter punishment, NOT simply because she is a girl, but because remorse is more likely to be shown by a girl.