You might want to fence in a small area in the coop and in the run if you can, so she and the rest of the flock can see each other but they can't get to her. Then let her out for the day with everyone with supervision so you know she isn't being singled out.
I give my birds treats always have they are very healthy. It's really up to the individual that has the birds from hatch to old age if you want to keep them around till then [I do] what you offer in feed and treats. My flock eats a balanced diet and they have to finish their main feed before the...