The double murder took place on Sunday night in the heart of the busy Vasco town near here, police said.
The accused, Pratima Naik, had earlier told the police that a gang of robbers killed her mother-in-law and sister-in-law and attacked her, before decamping with the booty.
During the probe, the needle of suspicion was on Pratima, who survived the attack, as she consistently changed her statements before the police.
Police are now on the lookout for the two other persons hired by Pratima to killed the two women.
The killings were the fallout of a family feud, Garg said.