J.J.
I would just tell her that hitting isn't nice and forgiving her is better then hitting back. If it continues then perhaps she need not play with her. But, atleast she got to see the little girls mom discipline her so there was a chance for both of them to learn hitting isn't right.
Hugging and conferting her is good. But, help her learn forgiveness I hope the other mom asked her to appologize that would give both them a chance for forgiveness.
GOod luck.