Gracie Nash is the daughter of Nash, the patient who House was stuck in a room with in the Season 6 episode Lockdown . She was an unseen character.
Nash had been estranged from his daughter since she was very young as she moved out with his ex-wife when he cheated with a student. As he lay dying, he told House he was waiting until 9 p.m. when she would be home. However, when he called, Gracie was out. When Nash hung up, House realized that he only called to listen to her voice on the answering machine and that he knew she would be out at work. He convinced Nash to call her back and leave a message about how he felt about her.