Maybe she'll be embarrassed and apologise for her behaviour. It will be pretty easy to move on then (just accept the apology if you want to and put the nastiness behind you). If she doesn't apologise, I don't know. You can try and be understanding if you want but if she was very mean or hurtful then you don't have to, period or no period. That said if she is particularly emotional right now, then she might be more sensitive or upset when confronted, so maybe leave it a couple of days.