In Feb 2021 Vietnam had a far lower case rate compared to Singapore so there was absolutely no reason to restrict entry from that country. In addition more than 5 months have passed since she arrived which is 10x the incubation period so there is no way she could have been infected at the time of arrival.
She was obviously infected by filthy disgusting sinkies who took advantage of her. I would advise her to commence a law suit against a whole bunch sinkies who flouted the Covid guidelines by crowding around her at a KTV lounge instead of following the rules.
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