Someone with a chronically dislocating shoulder that doesn’t respond to conservative (nonoperative) care is usually a good candidate for surgery. But (and that’s a big “but”), a history of noncompliance with their physical therapy is a red flag.
When there are psychological problems, the risk of treatment failure is very high. Likewise, failure to cooperate with the rehab therapy is a cautionary flag. Patients who don’t go to their appointments and/or who don’t participate fully end up with failed a surgery. Understandably, surgeons are hesitant to consider these patients as good surgical candidates.
It wouldn’t hurt to go with your sister to a follow-up appointment and ask a few questions. There may be come missing information to complete this story. It may also be possible for you to help her participate fully in the recommended physical therapy and see what a concerted effort can do for her.