This does sound consistent with IB. Outbreaks of IB typically affect the entire flock so it is a bit unusual for a single hen to be affected. The good new is that if she has indeed recovered from IB, her egg lay rate/ shell quality should return to normal but it may take up to two months...
Humm... Typically I dose Calcium gluconate, 5 - 10 mg/kg as an injectable in the muscle or under the skin. Vitamin D3 is administered at 200 IU daily for 3 days per week. I would discontinue the calcium as it has been several weeks without improvement. Calcium supplementation can result in...