Gurbani, who turned 17 this month, shot another steady three-over 73 at the BPGC to total six-over 216. Her earlier rounds were 70 and 73.
She was a comfortable winner over current Order of Merit leader Aditi Ashok who shot a 77 on final day. Aditi, still 14 years of age, totaled 223, finishing just one shot ahead of Gursimar Badwal (73) who ended at 224.
Amandeep Drall (79) at 226, Raksha Phadke (73) at 228 and Seher Atwal (76) at 230 occupied the fourth to sixth places.
Gurbani, who has already won the Usha Southern India and Usha West Bengal titles this season, is chasing Aditi for the Order of Merit honours and this win will further close the gap with two more tournaments, including the flagship event, the All India Amateurs, yet to come.
The winner, Gurbani, had four bogeys and just one birdie, on the par-4 14th in her round. Aditi five over after four holes with two double bogeys never had a chance and she finished with a 77.
Gurbani also topped Category A with Raksha Phadke second, while Aditi Ashok topped the Category B, where Seher Atwal was second.
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In Category C, Arushi Pandey (81) emerged winner with a total of 251 and Dhrishti Karumbaya (87) was second seven shots behind.
In Category D, Tanishka Kumar (86) topped with a total of 244 and Tiya Choudhary was a distant second at 269.
There are only two more events left with the Usha Maharashtra Ladies and Usha All India Amateur.