Close on her heels, half a point behind, are Padmini Rout of Odisha and Swati Ghate of LIC with 4.5 points apiece.
Playing white, Soumya defeated Neha Singh of Bihar in a Ruy Lopez opening.
Defending champion and top seed Padmini sailed through comfortably with black pieces against Priyanka Nutakki of Andhra Pradesh in a Grunfeld defence.
Playing attacking chess, Swati Ghate of LIC sacrificed her rook for bishop to weave a mating net around Pratyusha Bodda's king.
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Swati played the resulting endgame with queen against a rook and bishop with precision to net the full point.
Former National champion Tania Sachdev's miserable form continued as she lost yet another game -- this time to WGM Bhakti Kulkarni of Goa -- with white in a Queen's Gambit Tarrasch variation.
World under 14 girls champion R Vaishali of Tamil Nadu showed her class to get the better of her state-mate K Priyanka with black in a Scotch opening.