I hope your hen is feeling better right now. Sometimes, after feeling very sick due to egg laying issues, my hen would enter a partial molt which allows her to stop laying for a bit, Sorry, no experience with lice as it’s not something my chickens than free range during the day tend to get (worms, on the other hand…). I did hear of people that had luck with minor lice infestations with dusting of diatomaceous earth. It might be that only minor care is needed until she’s feeling well enough to dust bathe.