The woman, employed with a browsing centre at the suburban Adambakkam, was attacked last month while she was alone there by Vijaya Bhaskar. He splashed acid on her following an altercation.
The accused has already been arrested and lodged in jail, police said.
The victim's brother said the family was aware of the relationship between his sister and the accused and had approved their wedding proposal.
However, Vijaya Bhaskar was doubtful that the family could go back on their decision and therefore was compelling the woman to marry him, he alleged.
On February 12, a 23-year-old B Tech graduate working in a private firm died at a hospital following severe burns she suffered in an acid attack at a bus terminus at Karaikal on November 14 by a construction worker, whose overtures she rejected.