Mallika was missing since June 12 and her body was found with strangulation marks in Villupuram district, around 160 km from here, the next day and identified yesterday.
Cracking the case, police arrested aide Sathya, her relative R Ganesh and car driver S Karthik for allegedly murdering Mallika and recovered 35 sovereign of jewels taken away from the victim.
Police said Sathya and Ganesh strangulated Mallika on June 12 itself in moving car near Chengelpet, about 50 km from here, with Karthik at the wheels.
Karthik was initially hired by Mallika on an adhoc basis, known as "acting driver", but later continued to serve her for seven months.
"The victim did not cross check the antecedents of Karthik before employing him," a police official said.
A woman and her daughter were murdered recently at Maduravoyal here by an "acting driver" for gain. In that case too, the antecedents were not verified.