How old is she? Maybe it is the picture, but her comb/wattles look rather pale also if she is laying age...this time of year it is not unusual for birds to be molting, though from that picture she doesn't particularly look like that. DE is not going to do much if you already have a mite/lice infestation. Have you taken a good look at the bird(s) and coop and found anything? If you think you have a problem you might want to go ahead and treat the birds and coop with something like Sevin & Frontline/Ivermectin etc. Those little brown spots on her face are feathers right, no stick tight fleas in the area?