Poor thing. We have been through this so many times and it is not fun.
I wouldn't give her any milk or milk products as they can upset the stomach. Breastmilk is okay, though if you are still nursing.
Push fluids....water, pedialyte, popsicles, gatorade, Crystal light, koolaid. Pedialyte is the best by my daughter couldn't stand the taste of it so I would always try several different liquids
Don't worry so much about food. But, if she seems hungry then bland stuff works best....crackers, toast, rice
Since it has been going on for so long and she is still pretty young I would see if your doc has Saturday hours or if she hasn't had very many wet diapers (can't remember how many they are supposed to have) then take her in to the ER.
Good luck. I hope she feels better soon!