The deadly confrontation happened at 161 West 35th Street near 7th Avenue.
The 41-year-old woman was a worker at the salon called D' Galinas Center.
Investigators remained on the scene Thursday night looking for clues.
Witnesses said a woman ran out of the salon around 3:30 p.m. and flagged down a police officer.
The victim was rushed to Bellevue Hospital where she was pronounced dead.
The killer remained at large.