Prerna faced stiff resistance from Nidi Chilumula of IOCL before prevailing 7-5 6-3 at DLTA Complex.
Prarthana Thombare levelled the tie for IOCL with a 7-5 4-6 6-3 win over Sneha Devi Reddy.
In the deciding doubles, Prerna combined with Sneha Devi Reddy to beat Prarthana and veteran Rushmi Chakraborty 6-2 6-4.
In the Men's Team Championships, Oil India beat hosts EIL 2-0. IOCL also beat HPCL (2-0) and ONGC beat NRL by a similar margin 2-0. Defending champions GAIL received a bye into the Semi Finals.