The woman suffered severe injuries when she fell through the gap between two coaches and could not get back onto the platform.
The moving train ran over her left arm, severing it near the elbow, police said.
She also sustained head injuries and required 16 stitches.
She is currently receiving treatment at a hospital.
Woman objected to 'bad touch'
The incident took place around 7.15 pm when the woman was travelling home to Naigaon East from Borivali after visiting her sister in Goregaon.
According to the police, an unidentified man allegedly attempted to molest her during the journey.
After getting off at Naigaon railway station, the woman confronted him and demanded an explanation for his behaviour.
An argument broke out between the two.
During the confrontation, the woman reportedly threw her slipper at the man, and he reportedly threw his slipper at her in retaliation.
The accused then allegedly shoved her forcefully towards the railway tracks just as the local train began moving.
Moving train runs over her arm
The woman fell through the gap between two railway coaches and was unable to climb back onto the platform before the train moved forward.
The train ran over her left arm, severing it near the elbow.
Police said she also suffered head injuries and received 16 stitches.
She was taken for medical treatment and remains under hospital care.
CCTV footage helps police trace accused
Police examined CCTV footage from multiple locations as part of the investigation to identify the man involved in the incident.
Senior Police Inspector Ganpat Tumbada said officers arrested the accused on November 9, five days after the incident.
The accused has been identified as Jitendra Hirmukhe (53), a resident of Naigaon East, officials said.
The investigation is continuing.