The man, identified as James Antony, was arrested here today, police said, adding that he was upset that the woman, a divorcee, was not responding to his romantic overtures.
The woman, who is on ventilator support, has lost her eyesight while her seven-year-old son, too, is in the Intensive Care Unit.
The duo are undergoing treatment at a private hospital in Mangaluru in neighbouring Karnataka, police said.
Along with her father, the woman and her son were headed to a nearby church on December 24 when Antony attacked them dressed as Santa after he had waited for them, police said.