Dona Plácida is the seamstress, a former dependent of Virgília's family, to whom Brás Cubas entrusts the keeping of the little house in Gamboa, where he and Virgília meet. The natural daughter of a sacristan of the Sé and a confectioner, she supported her daughter and her mother with sweets, sewing, and lessons.
She accepts the role with difficulty, her eyes lowered for the first two months. Brás invents a tale of loves before Virgília's marriage, which she accepts entirely, and gives her five contos as a reserve. At the end of six months, "anyone who saw the three of us together would have said that Dona Plácida was my mother-in-law". She never agrees to sit at the table with the lovers and, when Virgília says that she seems no longer to care for her, she exclaims that she loves Iaiá and stares at her until her eyes fill with tears.
In a single scene the book lets her speak for herself: she tells the life she has had and confesses: "I was afraid of ending up in the street, begging for alms". She is the character in whom Brás's conscience accuses him most: he acknowledges having lowered her to the trade of go-between "through favors and money", but answers his conscience that vice is often the manure of virtue, and goes on to open the door to Virgília.
Ill, she becomes the object of a secret request from Virgília: that Brás place her in the Misericordia. He sends her there out of courtesy, and she wakes up dead. Brás concludes that her life served his loves, and he cites her in the final accounting as one of the deaths that fortune spared him.