Soumya (7.5 points) is just half-a-point ahead of Mary Ann after the 10th round as the leader faces Padmini Rout with black in a tough final round tomorrow.
Two-time defending champion Mary Ann, on the other hand, is paired against National junior girl's champion, 14-year-old Ivana Furtado of Goa.
In case both of them finish on equal points tomorrow, Mary Ann is better placed in the tie-break than Soumya.
Mary Ann outsmarted Swati Ghate with black in a Sicilian defence as the former was in total control of the position from the beginning.
Swati blundered her rook for knight as Mary Ann effectively utilised her extra material to win the game.
Unfancied Michelle Catherina of Tamil Nadu took the day's honours after upsetting Padmini in 86 moves in a queen ending.
Top seed Tania Sachdev had a fluent win against Kiran Manisha Mohanty to jump into the sole third spot with 6.5 points.
Results (Round 10)
WGM Swati Ghate (LIC) (5.5) lost to WGM Mary Ann Gomes (WB) (7); WIM Ivana Maria Furtado (Goa) (4.5) lost to IM Nisha Mohota (PSPB) (4.5); Michelle Catherina (TN) (3) bt WGM Padmini Rout (Odisha) (6); WGM Soumya Swaminathan (PSPB) (7.5) bt Bodda Pratyusha (AP) (4.5); IM Tania Sachdev (AI) (6.5) bt WGM Kiran Manisha Mohanty (LIC) (3.5); WFM G K Monnisha (TN) (3.5) drew WGM Bhakti Kulkarni (Goa) (4).
