I am guessing Northern Fowl mites. Could be lice too. Hard to tell from the pics.
Maybe the infestation is what has her down, I know if it gets bad it can kill them, they give up the will to survive. She may have had these for a while and gone unnoticed. Did you get some Sevin Dust on her? There is a video, you wear gloves, roll her on her back and just massage the powder in all over her, head, body, belly under feathers, until she is coated completely. I would have someone else due it due to you being pregnant, they shake and you can get the dust in your face, so have whoever wear a bandana or something over nose and mouth. i would get that done ASAP, or you can douse her in cooking oil like Red said, just grease her up feathers, skin, everything and let her be greasy for the day before you try to wash her up. The bugs suffocate. Or the dip, or something that will kill those critters fast. They usually don't just stay on one bird so be sure to check the others. Very common on their bellies toward the vent area.