Dianna was the clinic patient in Ignorance is Bliss that House used to get invited to Thanksgiving dinner with Cuddy.
In the episode Ignorance is Bliss, House wanted to be invited by Cuddy to Thanksgiving dinner, so, he went to the clinic for forty-five minutes. Dianna was in the clinic that day for unknown reasons, House was supposedly very nice to her since when they were finished, as they exited the clinic, Dianna thanked House telling him that he had been lovely to her, House told her that she was the one that had been lovely. Cuddy saw this thinking that House had changed so she invited his to dinner at her sister Julia Cuddy's house. However it was soon revealed that House may have bribed Dianna because he was rude to another patient but gave her twenty dollars to act like he had been a good doctor when she left the room.