Kassandra Bravo was reported missing earlier this month after she failed to turn up to a baby-sitting job at a family friend's house.
Police officers issued a missing person notice and three days later her body was discovered lying in a ditch beside a road near the village of Las Cocinas in Mexico.
According to detectives, it had been impossible to identify the body because her face had been stripped of her skin.
A post-mortem revealed that she had been strangled.
According to a friend, Bravo had been planning to tell her mother Angeles Bravo, 41, that her stepfather Daniel Murrieta Sainz, 42, had been sexually abusing her since the age of 15.
A police official said that Sainz had been brought for questioning and he admitted strangling Bravo and dumping her body, but he denied he had been abusing her or that he had skinned her.
The young woman's horrific death sparked an angry protest lead by Miss Bravo's friends.
Campaigners are demanding more action to protect women from violence and justice for the teenager.