D Bhavani, a first-year intermediate student, shut herself in a room at her house, doused herself with kerosene and set herself on fire at around 9.30 am, Hayathnagar Inspector of Police B Bhasker said, adding the girl died on the spot.
The girl was alone at the house as her parents and family members had gone to a nearby market to make purchases for Dussehra festivities, he said.
Bhavani had purportedly written (in Telugu) on the room wall that she was taking the extreme step as "there was a failure in declaring a separate Telangana state and no one was responsible for her death", police said, adding that a case has been registered.
The incident triggered protests with suspended Telugu Desam Party MLA Nagam Janardhan Reddy, who visited the girl's family, and villagers holding road blockade on the Koheda-Vijayawada state highway.
Some pro-Telangana activists also allegedly pelted stones on private buses.
A pro-Telangana student Ravinder, who set himself on fire in Medak district reportedly for the cause of Telangana, had succumbed to his injuries at a hospital in Hyderabad on Saturday.
Pro-Telangana organisations and groups claim that over 600 people, mostly students, have ended their lives in support of the demand for separate statehood since November 2009.