The deceased has been identified as Pramukhada Gavar, a resident of Juhu Lane in Andheri.
She consumed 62 tablets at around 2.10 pm, said police.
The girl was taken to nearby hospital where doctors declared her dead on arrival, they said.
An accidental death case has been registered at DN Nagar police station.
The reason that drove her to commit suicide was not known yet, police said.
Further investigation into the matter is underway, they added.