First, she's probably already somewhat dehydrated. Unfortunately, water right now may make her even more ill. Try a bowl of a FEW (2 or 3 at a time) ice cubes instead of water and most importantly CALL A VET!
Most vets offices have an emergency answering line that will have a vet call you back. If you're near a larger city there is a good chance that there is at least one emergency vet office open all night. If you don't have a regular vet to call, look in the phone book or do an online search for vets in your area. If nothing else, call the operator in the closest big city and ask for the emergency vet number to to talk to them for further advice.