It is not known if the teenager had been suffering from an underlying health condition.
Her death brings to seven the number of people from Northern Ireland who have died while suffering from the virus.
Orla O'Kane, 14, became ill last Sunday evening and was rushed to Derry's Altnagelvin Hospital, where she was pronounced dead shortly afterwards.
SDLP MLA Pat Ramsey said the teenager's family only learned she had tested positive for swine flu yesterday - two days after she was buried.
Mr Ramsey said the family was particularly distressed at the delay in hearing the news because a brother of the deceased had now contracted the virus.
'I understand the Department of Health knew on Thursday - the parents should have been the first port of call to protect themselves and others around them,' he said.
