Your roo could be ' over mating ' her. Roos , no matter what their size and stature , will often select a favorite hen or an easy target. Mites and lice are often difficult to detect and some birds are more affected than others. Check around her vent area and then about 2 inches above the vent, for egg casings along the feather shaft.
Finally , check your feed bag and be sure that it contains methionine. Birds that are deficient in this amino acid will eat their own feathers and that of others in an attempt to satisfy their craving .
http://msucares.com/poultry/feeds/poultry_feathering.html
Sorry it took so long to get back to you on this but I've had my hands full lately with this among other things.
I checked the feed (Purina Flock Raiser) and it does have methionine in it, so we're good there.
I found no evidence of parasites, or anything to demonstrate that the Silkie rooster that is in with them had been rough in any way.
I did put everyone on Rooster Booster, suspecting some other possible vitamin deficiency and I am happy to say that not only did
Estaline's saddle feathers grow back, but so did Daisy's.
Their combs and wattles went from a faded look, to rich red.
After a time of getting no eggs at all from Estaline, they're both laying.
We've gotten two eggs, two days in a row which hasn't happened in a long while.
We do still have an issue with one of the girls and slow crop or something similar, but everyone is peppy, eating and drinking.
I was thinking about putting them through another round of dewormer to make sure the blockage isn't due to internal parasites.
Short of that I'm not sure where to go from here, but I'm tickled the girls appear to be out of the woods.
Thank you for your wisdom!