The incident occurred on December 9, when the 16-year-old girl allegedly hanged herself at her house in Mumbra and left behind a suicide note, a police official said today.
The Kalwa Police had initially registered the case as accidental death before it was transferred to the Mumbra Police.
During investigation, the Mumbra Police booked the 17-year-old for abetment to suicide under section 306 of the IPC, said police sub-inspector P A Pore.
As per preliminary probe, both the teenaged girls were in love with a same youth from their locality.
"On the day of the incident, the 16-year-old called up her two friends and informed them that she was going to kill herself. She left a suicide note blaming the 17-year-old for interfering in her affair with the boy," Pore said.