Symbolism, Imagery, Allegory
You might have caught on to the fact that Koly always busts out a dowry quilt whenever someone gets married. It turns out she learned how to embroider from her mom, and it's a family tradition: "like her maa before her, and her maa, and as far back as anyone could remember, the women in our family embroidered" (1.10). Right away, then, we can understand Koly's dowry quilts as something that connects her to her familial lineage no matter where she goes in the world.
Importantly, there's nothing simple about Koly's designs. Everyone is impressed with her unique embroidery—even Mrs. Mehta whose mission in life is pretty much to be unimpressed by Koly. The dowry quilts make it clear that Koly is someone with considerable skills, and later on, once Mrs. Mehta ditches her in the city, these skills help Koly truly attain independence.
In the end Koly makes a dowry quilt for herself, and when she does, she explains its placement in the lineage of her quilts:
Once again I began a quilt for my dowry. My first quilt was stitched as I worried about my marriage to Hari, the second in sorrow at Hari's death. Chandra's quilt was stitched to celebrate her happiness. This time as I embroidered, I thought only of my own joy. (11.44)
Koly's made a dowry quilt before, but it wasn't awesome since her new hubby died of tuberculosis so soon after their wedding. Now it's her time to be happy, and to this end, the quilt she sews is full of wonderful memories and stories from her newfound joy.