In America, the social image of a spinster is shifting somewhat, so there's this interesting duel image going on. On one hand, a spinster is thought to be old, bitter, asexual, possibly a school teacher, possibly possessing many cats, possibly someone who was betrayed in love and never got over it, someone who is involuntarily unmarried, and just not any fun. A spinster is also an outsider to social norm typically.
But now we also now have images of strong career women who enjoy having sex, who enjoy having a career, who enjoy their friendships, don't care to be married by choice, and like things just the way they are. Think Samantha from Sex in the City.
But in America, 35% of women between the ages of 25 and 59 are unmarried, and in India the number is much smaller, only 10.5% of women are unmarried in that bracket.
In India, there is no word for "spinster" yet, and there is a positive image associated with being celibate. There is special space and respect for unmarried women in Indian culture. Being unmarried is considered voluntary, not involuntary and it's not considered a failing on the unmarried woman's part.