Here's what I'd do if I were you.
1. Give her a nice bath. Chickens like the spa treatment IMO. A 5-gallon bucket to wash and one of clear water to rinse. Rinse well. You can add a bit of vinegar into the rinse water. Lots of information on bathing chickens -- mostly probably under getting ready to put them in a show.
2. Dry her off well and keep away from drafts and cold winds when she's wet. You can towel dry her or even go so far as to use a blow-dryer on her feathers. She will look fluffy and beautiful when finished.
3. Consider adding vinegar to her water at the rate of 1TBSP to a gallon. This helps the pH in the chickens gut. Also helps absorb calcium.
4. Consider a vitamin in the water -- one that has probiotics.
5. Keep an eye on her -- she may need a bath from time to time.
Good luck