Police had earlier called for calm after the riot broke out on Thursday evening in a housing estate.
Harrowing witness accounts on social media suggest the victim may have been hit by a stray bullet aimed at police, The Sun reported.
Local council candidate Emmet Doyle wrote: "A masked figure stopped at the bottom of the road and fired shots up towards the [police] Land Rovers.
"We all turned and ran, I stopped beside the land rover nearer the top of the street and a girl beside me dropped to the ground."
BBC reported the trouble began when authorities raided properties in the area, with its Northern Ireland home affairs editor Hulian O'Neill said dissident Republicans are being blamed for starting the unrest.
"Happened during disorder following police searches," he said.
Sky News UK senior Ireland correspondent David Blevins said there had been an ominous warning days ago from Republicans.
"Earlier this week, they said police would be to blame for any disorder this year and warned what they called 'British crown forces' not to saturate the area," Blevins said.
"Despite the fact that we are 21 years past the Good Friday Agreement, 26 years into the terrorist ceasefires in Northern Ireland, dissident republicans, renegade republican groups still oppose the peace process and the threat level posed by them has never been deemed less than severe in Northern Ireland - remember just two months ago they detonated a car bomb in this very city."
Leona O'Neill, a journalist for the Belfast Telegraph who was at the scene, said she called the ambulance for Ms McKee after she was shot.
"I was standing beside this young woman when she fell beside a police Land Rover tonight in Creggan #Derry," she tweeted.
"I called an ambulance for her but police put her in the back of their vehicle and rushed her to hospital where she died. Just 29 years old. Sick to my stomach tonight."
