"The woman had attempted suicide by consuming poison near her college last Wednesday as she was being harassed by the 23-year-old man," said Matunga police station senior inspector, Balasaheb Kakad.
The victim, whose name is withheld by police, breathed her last in Sion Hospital in morning.
The accused, identified as Ilaiyaraja Velpandi, was arrested on Wednesday itself.
Following the woman's death, police today added section 305 of IPC (abetment to suicide) against Velpandi who was earlier booked under the Protection of Children from Sexual Offences (POCSO) Act, Kakad said.
"On last Wednesday, Velpandi accosted the girl and asked her to marry him, the officer said.