Luisa is constantly at Alfredo's side when he is sick. The doctors believe Luisa does not understand English, but when they mention that Alfredo might die, she overhears and starts crying out and they realize she does understand some of it.
Later, the doctors overhear her arguing with her younger son Manny.
Gregory House finally needs to know where Alfredo works on weekends and confronts Luisa in perfect Spanish (claiming "I have no idea what I just said"). He has realized she and Manny were arguing about Manny taking Alfredo's place so he wouldn't lose the job. He learns just enough to direct the rest of the team to search for cock fights.