The main theme of this story is the powerlessness of girls in India to make their own life decisions. The eNotes article on Themes and Characters (linked below) has an excellent discussion of this issue. Not only do their parents choose their husbands, but also the husband can decide his wife is unfit and get rid of her (sometimes by burning her to death). In the same eNotes article, you will find the answer to your question about Koly's characteristics. You might sum it up by saying that she longs for independence, but she is a victim of her strict culture.