Millie, winner of the Usha Northern India Amateur Championships earlier in the season, shot one-over 70 and took a handy three-shot lead over the reigning champion and playing partner Aditi Ashok (73).
Gurbani, who is one point ahead of Aditi in race for Order of Merit, was one shot further behind at 74 at the par-69 Tollygunge Golf Club.
The top-three will play together in the second round, following which the top-16 will qualify for the matchplay section of the tournament.
Ridhima Dilawari and Gursimar Badwal were tied for fourth at 75 each while Tvesa Malik, Astha Madan and Amandeep Drall carded 77 each.
The top three girls found the front nine of his lovely course rather difficult to negotiate and had no birdies over it.
Millie, who had just one bogey on par-5 seventh holes, had two birdies