Like her husband, she is seen in the prolog, and in the family photo that Fran finds. On this, she has short brown hair and wears a dress with a tiny symbol at the collar. Her dress is slightly lighter compared to her sisters and her dress's collar is white while Grace's is black, perhaps hinting at their opposite personalities, with Lucia being good and Grace being evil.
Not much is known about Lucia as she is dead at the start of the game. However it is implied through dialogue with Grace in chapter 5 that unlike Grace she resented Dr. Oswald to an extent, and feared that he would try to keep her away from her daughter or even kill Fran. This is likely what motivated Dr. Oswald to request the help of Remor in "taking care of" Fran's parents so that he may, with Grace's full approval, extract Fran's brain from her head for further studies. It is unknown why Lucia turned out relatively sane compared to her sister, or why Grace almost seems to idolize or have romantic interests in Dr. Oswald but it can be assumed that it stems from events occurring in their childhood at the asylum. It is also unknown whether Lucia and Grace like Mia and Clara were surrendered to the asylum willingly by their parents, taken due to some mental issues making them a danger to others or themselves, or whether they simply went for regular appointments and went home afterwards.