I would advise looking for a new doctor. One whose a little more up with the times as far as breastfeeding research goes. I can't believe your Ped. told you not to nurse even when your child was dehydrated. You need to be nursing and nursing often. Babies this age that are still nursing are very lucky when these stomach bugs hit because mom can nurse them to keep them hydrated and get them sustaining nutrients at the same time. I think your pediatrician is assuming that the lactose in breastmilk is the same as the lactose in cows milk, which is utterly (no pun intended) ridiculous. I can't believe a doctor in the 21st century would believe that. Your child needs that breastmilk now more than ever. Everything about breastmilk is specifically tailored by nature to be the best for baby. Especially when they're sick.
Our family just got hit by this bug a week or two ago and my 17month old son wouldn't eat or drink anything except breastmilk for days. He was very sick, but the milk I was able to provide for him kept him hydrated and kept up his energy while preventing weight loss. Let your daughter nurse for as long as she likes. Especially if you're worried about weight loss. The first milk they get is watery and good for thirst and dehydration but the hind milk they get while they're nibbling at the end of a feeding is chock full of beneficial fats and will help fill up her tummy too. Also, your breastmilk is full of antibodies that your body is producing to fight off this illness and that will only help her get over it quicker. And another thing, your breastmilk is also full good bacteria that her GI tract needs in order to regain the balance of beneficial flora for proper digestion.
My advice is to nurse, nurse, nurse. If you're nursing enough, you don't need to worry about things like pedialyte. Actually, if you're nursing enough, you don't even have to worry too much about solids for a few days. My sons always recovered better when I stuck to breastmilk and let them tell me when they were ready to eat something solid.
Best of luck to you, and don't long for the nanny too much, babies need mommy's TLC more than anything when they're sick :)