ECATEPEC, Mexico — Itan Flores was a young teenager when her first boyfriend imprisoned her for six weeks in a room furnished with just a mattress and a radio. He returned only to rape her, she said, often withholding food and water.

She escaped when he forgot to lock the door one day. He told her that if she ever reported what happened to the police or to her parents, who thought she had gone voluntarily, he would kill her family.

“To this day, my parents do not know I was a prisoner,” Ms. Flores, 24, said, her eyes welling with tears. “For a long time I thought it was all my fault.”

A new generation of Mexican women has taken to the streets in recent months to banish the idea that somehow — with their clothing, their demeanor, their whereabouts — they provoke the violence they suffer. That attitude is so entrenched in society that it extends to the police and the courts.