If she has lice, I'd be willing to bet that there are mites in the coop, too, so it also needs to be treated. Shampoo will work, but if she is sick, bathing her will just stress her out.Ah, yep, lice would do that. If a chicken is infested enough, they will become so irritated that they won't eat or trick and just sit there. As long as you don't feel anything inside her abdomen, then the lice are definitely the problem. Everything casportpony mentioned is good to use. But if you can't find any of that, you can also try some flea/tick shampoo for dogs and cats.
-Kathy