Good that she is interested in eating something. What kind of bread you are feeding her, if it is the organic sprouted grain bread (Ezekiel brand?) or another grain bread with seeds? That's better than regular bread. Don't use regular bread, too much can cause more serious issues in a bird's crop, yeast & sour, etc.
Please do what you can to get rid of those mites asap. Cold Winter weather makes it a bit more of a challenge, I hate to use anything liquid this time of year.
A few years ago I did rescue one chicken and she was loaded with bugs. I actually brought her in, gave her a bath in the tub with tea tree oil shampoo, lathered her up from the neck down, then let it sit on her several minutes, then scrubbed those nasty bugs off, rinsed well with warm water. She was a sweetheart & let me! I actually filled the sink with warm water and set her in it, getting all of the soap off, she was a rare one, didn't even flap, was gently pecking at my ring! Then I towel dried her off, & dried her the rest of the way with the hair dryer on low. I set up a large bin with fresh wood chips in the bathroom & she nestled right down for the night. She spent the night in my spare bathroom because I did not want her to catch any cold. The next morning I checked her over, no mites! Sometimes mite eggs are still embedded in feathers & hard to see, & could hatch out days later, so I also sprayed her with the Bronco spray which is permethrin based, dried her again, then took her to her new coop & pen. She takes regular dust baths & has not had mites since. She is a much happier chicken, especially compared to the horrible place she used to live.
I know you are doing your best for your hen.

Get rid of those mites & get her to eat more.