The 20-year-old student was sent to a quarantine centre on June 4 and developed symptoms such as a cough, runny nose and diarrhoea that same day.
Tests showed she has the N501Y mutant strain of coronavirus, as does her 17-year-old sister and mother.
None of them had been vaccinated against Covid-19.
The Centre For Health Protection also recorded another six imported cases on Monday, including four people who flew in from Indonesia, one from the United Arab Emirates and one from the USA.
There was also a handful of preliminary positive cases.