Owie! Poor little thing! Definitely keep her separated. I would not put anything on it right now. You'd be amazed at just how tough chickens are, but since she's just a youngin, you'll want to watch her. Give it a couple of days (1-3) to air out and dry, make sure it's clean by taking a lint free cloth in warm water and just squeeze to "rinse" the area ONE TIME! Meaning you don't want to repeat it day after day. You want the skin to stay dry. And she should heal fine after a couple of weeks.
*OPTIONAL* To Expedite Healing:
Once the skin starts to dry out, you can make a Calendula tea. Boil a couple of cups of water and turn off the heat. Once the water has settled to a steam, throw in about a handful of Calendula flower petals and let sit for about 25 minutes. If you have Aloe Vera JUICE you can add some of that too. You can then take a (lint free) rag and then rinse the skin with it for a few more days and she should start to heal very well.
Make sure you only use Calendula Officinalis. It's common name is Marigold, but only the flowers with the Bright Orange flower heads contain healing and soothing properties. I'm an herbalist and have raised many a critters and always run for the "farmacy" before the drug store.
Keep us posted on the little one! May she get better real soon!
Many Blessings!
Tracy