The girl, identified as Rajpriya Sinha, was staying in Delhi with her uncle, who is a former Bihar legislator, and his family. She was a class 12 student at a private school in south Delhi, said a police official.
So far, no foul play is suspected in the incident, the official said.
According to the police, the girl had held a get together for her sister and close friends yesterday night when the adults were not home. She came to the balcony around 2.30 AM to check on a friend, who had just arrived in an auto-rickshaw, when her foot slipped and she lost balance.