Mrs. Nguyen is the mother of Diane Nguyen, she shows resentment to Diane for moving to California and breaking off contact with her and the rest of her family. Aside from her daughter, she has four sons. Marty, Artie, Tommy and the adopted literal black sheep Gary. Like the rest of her family, she is often verbally abusive to Diane and regularly insults her whenever she can. She lives in Boston, and she is widowed from her husband, who died in 2014.
Much of her actual background is unknown, but she's lived in Boston, Massachusetts since the 70's. She had five children, one of them a adopted black sheep. During Diane's childhood, her mother, similar to the rest of her family, would verbally abuse her and mess with her. They didn't seem to care much about her, however, when she left to go to Hollywood, Diane's mother called her and showed anger towards her for leaving the family.
Her only major appearance thus far was in Live Fast, Diane Nguyen. Diane and BoJack Horseman, while Diane was ghostwriting his biography, traveled to New York to meet Pinky Penguin, who's publishing company was making the book, while there, Diane heard news from her family that her abusive father had passed away the previous night, her and BoJack went over to Boston and met the family. Her mother immediately showed resentment towards Diane and told her off for abandoning them. She was disgusted by her brothers and their constant pranks and messing around, they claimed to appreciate her but still shouted at her and abused her verbally. BoJack, who grew up without siblings, took a liking to them and they began hanging with him. Diane arranged the entire funeral for her father, however, only Diane and BoJack even showed up. Diane and BoJack confronted them, and their excuse was that their father wouldn't have wanted a funeral, he would have rather preferred to be chummed and thrown in Derek Jeter's face, so they chummed his corpse. When Diane's mother and siblings began yelling at her for abandoning them, BoJack tried to help her out, but ended up making thing worse, causing them to make fun of her for being a freeloader off Mr. Peanutbutter. Diane freaked out, took her dad's chummed body and drove off. It later went off rolling into the street, hitting a old lady, which Derek Jeter then stole her wallet.
They returned in The BoJack Horseman Show (episode), which took place in 2007. Diane's mother called Diane, who was working at a Starbucks in Los Angeles. She was clearly upset Diane left.