It is really difficult to answer your question, without details of the course after surgery and the reports of the latest investigations. You have not mentioned where the pus is. If it is inside the abdomen (tummy) they will have to perform surgery to drain the pus; but without complete details of the site and amount of pus, it is difficult for me to answer in detail. If your aunt went to Saudi Arabia 4 weeks after surgery, she must have been OK and the doctor who operated upon her must have seen her, before permitting her to leave. So this pus may be unrelated to the surgery.