Plain yogurt is fine for probiotics mixed into egg or some feed. I would not give her more than a teaspoonful a day. She can be out of her crate during the daylight hours for up to 8 hours a day, walking around, eating. Just don’t let the other chickens get close enough to her to peck her. If she is in the crate with them, she may enjoy hanging out with them during the day. If there are a lot of flies, keep her inside though, since flystrike (maggot infestation on wounds or prolapse) would be more serious. Once she stops laying for a few days, which can take 3-4 days since eggs are being produced continuously, then you can stop keeping her in the dark.