The victim was celebrating her birthday today.
Sajid, the accused, brought her a cake, and later took her to the building's terrace to discuss something, police said.
They had a fight as Sajid suspected that she was going around with someone else, and in the middle of it he allegedly pushed her off.
The woman fell on the asbestos sheets atop an adjacent house and survived, though she suffered injuries, assistant commissioner of police K Shiva Kumar said.