The woman, identified as Sakshi Parekh, is a housewife. She also suffered injuries in the incident and has been arrested.
The mishap occurred at about 11 AM at Mahavir Nagar in suburban Kandivali when her Honda City car rammed into a motorcycle and then a road divider before dashing two auto-rickshaws, coming from opposite direction, they said.
The biker Dilip Soni (30), who was seriously injured in the accident, died while undergoing treatment at Bhagwati Hospital.
"The housewife says she accidentally pressed the accelerator instead of breaks, which led to the accident," the DCP added.
She was arrested for rash driving and her blood samples were taken to examine if she was under the influence of alcohol while driving, police added.