Even as Aditi carded the day's best, Gurbani, who had a stunning 64 on first day, went up to 73 on the second day.
Gurbani leads the field with a total of three-under 137, while Aditi is at three-over 143.
Astha Madan (74) stayed in third place with 147. Sehar Atwal and Millie Saroha were tied fourth after repeating their first round scores of 75 each. They were at 150.
Gurbani began with a steady string of five pars, but a double bogey on par-3 fifth and a bogey on seventh meant she was three-over for the front nine.
She finally got her first birdie on the 13th and then had one bogey on 17th for a round of 73.
Aditi, who has played a lot in recent weeks, struck back with a fine round. She birdied the fourth but bogeys on fifth and ninth meant she turned in one-over.
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On the back nine, she had back-to-back birdies on 12th and 13th and then parred next four. But a bogey on 18th deprived her a chance of a under-par round.
Gurbani led Astha Madan by 10 shots in Category A, and Aditi led Sehar by seven in Category B.
In Category C, Arshia Mahant (89) dropped to second place at 170 as Arushi Pandey carded 79 to move to 166.
In Category D, Tanishka Kumar (77) moved into lead at 166 with Vasundhara Tihara (89) second at 176.