You can get a kitty safe shampoo at most pet stores. Avoid Hartz and flea and tick shampoos if possible.
Take a empty bottle, and put 1/3 shampoo and 2/3 water, shake well. Use that as your shampoo, so it will rinse out easier. Rinse super well.
Make sure she's dry thoroughly before you let her out where there is drafts or cold air, as cats are notorious for getting respitory infections.
Good luck!