So if I was her, I would have asked to get a written confirmation of this upgrade pledge from 'mgr Paulo'.
Seriously, what a drama for something that happened 20 years ago. Also, pretty typical "ma fan" locals attitude from Mrs. Chung of requesting something that goes way beyond 'returning the favor'. I mean, seriously, the entire family??? For some probably minor medical help offered?
Besides, if you know you wont be flying another CX flight in the next 20 years, then why not ask for something like a cash voucher or extra AM?