Hi,
It sounds like this lady has a neural traction injury. Her aggravating activities are at EOR positions which go away after a little while.
Presumably the osteopath has sorted the joint problems in the C/S.
However, some core stability work for the deep cervical stabilisers won't be wasted.
To test for instability, lie the patient supine. Palpate the transverse processes bilaterally. Ask the patient to FF to 90deg - that is her arm to the ceiling. Then ask her to slowly horizontally extend the arm - that is move the arm from the ceiling to parallel to the bed. If she has instability, you will feel the TP rotate towards the bed into your fingers. Try it on people without neck pain to get the feel of what stable is (assuming they have a stable neck!).
Try and let us know...