Leonne Weeks was stabbed to death on a path just off Lordens Hill, Dinnington, in January last year.
A post mortem examination revealed she died of multiple stab wounds.
Shea Peter Heeley, 19, of Doe Quarry Lane, Dinnington, admitted murder and was warned he would be jailed 'for a very long time indeed'.
There were angry, emotional outbursts from the public gallery during the hearing, where two men stood up and shouted at the defendant.
One man warned Heeley that he would face revenge for his brutal actions.
He said: "Wait until the day you come out, I promise you now I will do the same to you. Wait until you walk out of jail, I will wait."
Heeley, dressed in a black hooded sweatshirt and tracksuit bottoms and flanked by a number of security guards in the dock, showed no emotion during the hearing at Sheffield Crown Court and spoke only to enter his guilty plea.
Judge Paul Watson QC, told him the mandatory sentence for murder is life imprisonment and warned him that he would be jailed 'for a very long time indeed' when the tariff is set for the minimum number of years he must spend behind bars before he can be considered for parole.
He said a 50 page psychiatric report had been produced which concluded that Heeley was fit to enter a plea.
"The conclusion is that there are no psychiatric diagnoses or disorders," the judge revealed.
Heeley is to be sentenced on March 5.