Thus she does not have a frozen shoulder, that is the first point of clarification.Her main Aggs are any movement towards end of range and lying on her affected side.
Think about the mechanics at the 70-120 degree mark. The AC joint comes to mind, as does subacromial impingment and tendinosis. Where exactly did the Dr place the steriod?
It may well be a tendinosis with subsequent rotator cuff tear. An MRI or diagnostic ultrasound would be of assistance in the diagnosis. It seems you are checking all the right places but if this issue has been there for 9/12 she might have quite a few secondary symptoms that are over-lying the main issue. Try releasing under the scapula (subscapularis), mobing the AC joint and SC joints just short of the painful range and perhaps tape to inhibit the upper trapezius. Then send away for 24 hours and get her back to recheck. Any increase in range will be progress.
Looking forward to hearing more on this one