Emergency services were called to a flat in Cathays at 6.10pm.
A statement has been released by The Marches School, where Miss Griffiths was formerly a pupil.
The statement said: "We are incredibly sad to have learned today that a former student of The Marches School has tragically lost her life.
"Lauren Griffiths was a talented student whose academic ability and contribution to whole school life made her a true asset to The Marches School.
"The teachers, support staff and students send their condolences to the family at this time.
"We will share information relating to Lauren’s funeral as soon as it becomes available."
On Thursday, South Wales Police said Miss Griffiths’ family, who live in the Oswestry area, are being supported by specially-trained police officers.
'A beautiful, bubbly girl'
In a statement released through the force, they said: “Lauren was a beautiful, bubbly girl. She loved being part of a large family and was a real people person.
"Lauren’s fun and unique dress sense always made her stand out in a crowd and she was comfortable and confident in her own skin.
“Lauren was taken from us too soon and leaves a massive hole in all our hearts.”
Detectives are appealing for anyone with information about the incident to come forward.
Those who were in Glynrhondda Street between midday on Monday and 6.10pm on Tuesday and may have seen or heard anything in connection with the investigation have been asked to contact police.
Detective Chief Inspector Mark O’Shea, the senior investigating officer, said: “South Wales Police appreciate the support given by the local community while our enquiries continue in the area.
“We ask anyone with information about the incident please to contact us via 101 or Crimestoppers anonymously on 0800 555 111, quoting occurrence 1900154230.”
Information can also be submitted at mipp.police.uk/operation/62SWP19A84-PO1