Speaking 20 years after she was last seen leaving a Bath nightclub, police said the discovery would help the investigation "significantly".
Miss Hall's remains were found at the side of a motorway slip-road in 2009.
Pat Hall said she would like to know "who it was" and why her daughter had been left "in such a ridiculous place".
Miss Hall, 25, who was a clerical worker at the Royal United Hospital in Bath, had been for a night out at Cadillacs nightclub when she was last seen on 9 June 1996.
A black bin liner containing her bones and skull was found by a workman clearing vegetation next to a slip-road at junction 14 of the M5, near Thornbury, South Gloucestershire, on 5 October 2009.
Nine people have been arrested in connection with the case since the investigation began but no-one has been charged.
Det Supt Andy Bevan said: "Through new techniques, we're in the process of developing a DNA profile.
"There's no doubt this brings us an important step closer to finding her killer."
Her mother Pat, from Bradford on Avon, said she would like to know "who it was and why" and why her daughter had been left "in such a ridiculous place, by the side of a motorway".
"It was just the fact that she had been found and left in such a public place with no dignity," Mrs Hall said.
"At least that allowed us to do that very last thing that a lot of us do for our loved ones, to actually be able to say goodbye in a dignified way."
Ms Hall's father Steve said they had realised within days that she was "probably dead or in serious trouble".
"Our lives have been totally altered and they can't be put back together completely," Mr Hall said.
"We're saying once again, someone out there knows something, someone could come forward with information which could solve this crime.
"I believe there are a number of people out there who probably know what happened to Melanie and the people involved and, for whatever reason, they've seen fit not to come forward."
Detectives say they are "a step closer" to finding Melanie Hall's killer after new techniques uncovered DNA on an item found near her remains.