For the most part I agree with the answers given. In addition to the obvious necessity of contact with her physician and/or PT for appropriate clearance, I would suggest that if she performs squats with a barbell, she hold the bar in front, not behind her neck. Holding the bar behind the neck requires significant external shoulder rotation which could be problematic. Also, if her PT concurs, internal and external shoulder rotation with the humerus at 90 degrees of shoulder abduction, using a light to progressively heavier elastic resistance is excellent for training the shoulder rotators.
Good luck, Daniel