Moushumi's parents were aqquaintances of the Ganguli family. She and Gogol met as kids, but she didnt take to him or any of the other children. She felt a little above them, to be honest. She had spent some time as a child in England, and always had a slight accent, despite being raised in America for most of her life. She has a deep passion for anything European, particularly of France.
After Gogol's fathers death and his breakup with Maxine, his mother thought it might be nice for him to meet a nice, Bengali girl-who happened to be Moushumi. Moushumi herself had a devastating breakup with her fiancee previous to their meeting which was the talk of the entire Bengali community on the East coast, apparently. Gogol only remembered Moushumi as the quiet girl who famously "detested" American television.
By this time, Gogol is settled in New York City, where Moushumi also resides. They arrange to meet in a swanky little cafe, where Gogol is immediatly taken aback by Moushumi. She sort of much transformed into this gorgeous goddess, with her cigarette and glass of wine. She and Gogol hit it off right away, and begin to start a passionate courtship. They eventually marry, much to the delight of all and begin, what they hope to be, a happy life together.
Things go well for a while, but quickly the two seem to drift apart. Moushumi begins seeing Gogol as a bore, while Gogol is too submerged in his own happenings to notice. Moushumi even gives up a fellowship in Paris to stay near Gogol iwthout his knowledge. This makes her feel that Gogol is becoming a burden in her life. Moushumi one day stumbles upon the name and address of a past lover. She wants to call him up, but is torn. It seems she still loves Gogol, but is not "in love" with him anymore. She finds a book given to her by that same lover tucked away in her bookshelf and begins re-reading it every night. This ultimately convinces her to call up her former lover, a Frenchman, and they begin a torrid affair. When Gogol finds out, they divorce.
To me, Moushumi was the most interesting character. She was like a bomb waiting to explode. As a child and well into her college years, she was very bookish, quiet, and reserved. She experienced life through her books, and became somewhat obsessed with European life. She wasnt particularly interested in her own culture, or fulfilling the standards and goals put on her by her parents or society. She was just different.
She never felt a mans touch until one small incident in high school, I believe, where an attractive teacher caressed her and told her how beautiful she was. She never followed through with it. I think she always regretted not channeling her true beauty or sexuality for so long. So after college she traveled to France and became free. She indulged in many affairs, and lived a fast paced, passionate life she never had yet always wanted. She finally felt liberated.
Back in America, she became engaged to a white man with whom she later broke up with and then met Gogol. Moushumi was a paradox. A shy, introverted girl turned into a mysterious, dark, and seductive woman. She seemed strong, yet underneath it all was painfully insecure and uncertain. I believe if there was a "The Namesake" part 2, Moushumi would be older, yet not wiser. She is an intelligent woman but would always be chasing after things, getting what she wants, but ultimately losing everything she chased after.