Unfortunately, the feathers wont grow back until she molts. The upside, not she'll stay clean and dry. What was probably happening was she would get a drink of water, into which her crest would go and get wet. Then, she'd head outside and scratch around in the dirt, resulting in the gobs of mud. My Silkies do that all the time, but its not usually super dirty, just a smudge here or there.
