So sorry you are so worried!
Well just so you know my doctor told us the same thing. As long as she is drinking and making we diapers she is staying hydrated. When she is ready to eat she will start eating and make up for all of the food she hasn't eaten.
The doctor told us when (by the way I have a 3yr boy and 2yr girl) they vomit and have diarrhea it is their bodies way of getting the virus out of their system to let it take its course. I know it is hard to watch her go through it. I can tell you everyone is right with sugar comes worse Diarrhea. You don't want that either.
Also with the crackers, Peanut butter is a good source of nutrients, try making peanut butter with saltines/Ritz. (copied from site: Besides being fun to eat and delicious, USA peanuts and peanut butter are nutritious! One ounce of peanuts is a good source of protein. According to the United States Department of Agriculture (USDA)* one ounce of dry-roasted peanuts provides more than 13% of the daily reference value (DRV) per serving. Peanuts and peanut butter contain several vitamins and minerals. Peanuts are good sources of vitamin E and B vitamins. A USDA report shows peanuts supply minerals such as calcium, copper, iron, magnesium, manganese, phosphorus, potassium, selenium, sodium and zinc.)
Hang in there girl! She will be fine, just keep the water coming/fruit two o (flavored water with no sugar added), might be a good replacement too! Good luck! A. www.busymomsworkathome.com