The deceased was found hanging from the ceiling fan of her room on the night of Wednesday.
"The girl's father, who works with a Hindi newspaper, found her body when he went to her room to call her for dinner on returning from office. She had left a suicide note on the table saying that the reason of her death is in a video message in her mobile phone," said a police official.
Her father told police that the trio, identified as Joginder, Sonu and their sister Sonu used to harass her daughter who was studying B Com via correspondence of Delhi University.
"They had beaten up the girl in August last year after which a case under sections 354 (molestation), 452 (House-trespass after preparation for assault) and 323 (voluntarily causing hurt) after which Joginder and Sonu were arrested. However, they were later released on bail," said a police official.
"We are examining the claims made in the video by the girl and her family in their statements," said a police official associated with the probe in the case.