It was most sertanly NOT Haruhi. As you recall she is a commoner and, before she entered Ouran, had never met the twins. That little girl was only a girl that went to their school... nothing else. Besides, judging by how old they looked, that was around the time haruhi's mom died so it couldent have been her! =]
i think it could possibly be her because her mom was a lawyer so they could have ben rich in the past thus them meeting in the snow. or maybe this scene was at a park not at school and thats how they use to meet or something (plus the girl did look like younger Haruhi) if so maybe Haruhi just didn't remember them?