Your subject is not in the experience stream of most who contribute to this forum. If I understand correctly the Nuss Procedure has something to do with strengthening one's bone structure, sternum is the target of this in the brief look up I read.
This suggests to me it is important that an effort continue to seek advice from the surgeon who did the procedure. I am surprised that the patient hasn't already received specific advice and restrictions, if any, on physical activities. For example, when my sternum was cut open to perform heart surgery, I was give very specific limits on physical activities for the first 4 to 5 weeks following the surgery. After that time all restrictions on me were removed. I tell of this experience to show my experience with getting specific medical advice, it do no suggest this advice be applied to your situation.
This is too important, I think, to get advice from anyone other than the professional who has "hands-on" and a full report on what exactly was done during the procedure.
I don't know why she wouldn't be able to. By then she should be able to get a hold of her doctor to ask that question as well!