That is know as pasty butt or pasting up. It can be fatal if not treated. Can you get some water out of your commode tank (not the bowl) which is clean, and warm it up to wash her bottom off with soapy water rubbing it with your fingers? A baby wipe would work also. Start dipping the chick's beak into water for a second, then letting it swallow each time. Check it daily, since it may happen again in the first week. Shipped chicks can get dehydrated and pasty butt is common. If you have some chick electrolytes and vitamins, use them in the water. Pedialyte works as well. A tsp of sugar dissolved in a quart of water can work too. As long as the others are acting alert, they should be fine, but make sure they are drinking. What is your brooder temperature?