My guess is that perhaps the flora in her intestines was wiped out by the virus and now her body isn't processing it like it used to. I would stick with the pedialyte and give her probiotics for a few weeks before trying something very gentle on her stomach, like some yogurt (because the milk proteins are partially processed) or maybe the similac sensitive since she tolerated that before, or even something completely non-dairy like rice milk.
My ped always told us to give the kids a probiotic after diarrhea, and also every time they took an antibiotic. He recommended Culturelle, and we would open an adult capsule and some of sprinkle the powder on food. One capsule would last 2-3 days.
Also, for what it's worth, my cow's milk sensitive child likes rice milk.
Good luck, and hope she feels better soon.