I would get her drinking by dipping her beak in a small cup of water. You can make some homemade electrolytes, or use Gatorade or Pedialyte. Electrolytes can be made with an 8 ounce cup of water, 1/4 tsp of sugar and a tiny pinch of salt. Watermelon is food for hydration. For vitamins human B complex tablets 1/4 tablet daily are okay. Most feed stores sell Durvet and Rooster Booster chicken vitamins, powders, and liquid vitamins. Poultry Cell and Nutridrench are good ones with electrolytes in them as well, and dosage is 1 ml per every 3 pounds of weight daily. Offer some cooked egg and watery chicken feed several times a day. What are her droppings looking like? Has she been laying eggs?