Flora is a divorced seamstress who now lives alone. She's hired to make Angela's wedding dress and once also made one for Violet Westing. She smiles all the time, especially in inappropriate situations, which makes some of the other characters question her behavior. While we find out pretty quickly that she had a daughter named Rosalie, we don't know what happened to her or why she's not around.
This smaller-scale mystery is solved later on in the novel when we learn that Rosalie had Down's syndrome, and died when she was only nineteen. It seems her death is connected to the Baumbachs' separation, just as Violet Westing's death was connected to her parents' separation.
The fact that Flora gets partnered up with Turtle for playing the game starts a real healing process for both of them. Turtle helps diminish the pain Flora feels at the loss of Rosalie, and Flora stands up for Turtle as a softer, kinder mother figure:
"All mothers think their children are beautiful. Rosalie was an exceptional child, they said, but she was the lovingest person that ever was."
"My mother doesn't think I'm beautiful."
"Of course she does." (11.6-8)
Their relationship becomes stronger and stronger over time—did you catch the aside that Flora ends up living with Turtle at the end of the book?—and shows that you can rebuild your relationships through a family you make, rather than just relying on the one you were born into.