According to Margaret Williams’ biography of Sophie (Saint Madeleine Sophie, Her Life and Letters), it was the fresco she found on the wall of the villina (the small villa up the hill from the larger Villa Lante) that convinced her to purchase the properties on the Janiculum Hill. We see this episode in Part 10 in the chapter entitled (appropriately!) “Mother of Sorrows.”
When construction projects destroyed the wall on which the fresco was painted, the Society commissioned the painter Pietro Gagliardi (1809-1890) to execute a reproduction of it in oils for the Villa Lante chapel. This painting (above) now hangs in a large room at the Villa Lante.
The novel also alludes to the fact that Sophie consecrated the Society of the Sacred Heart to Our Lady of Sorrows; this happened during her intense period of isolation after the Congregation of 1839. Sr. Margaret Phelan, the current archivist in Rome, writes that on the 12th of July, 1839, Sophie “consecrated the Society to her with a prayer recited before the fresco on the garden wall.”