Maria is the name of an unseen character in Facade. She is a client of Trip's from Barcelona whom he admits to having had an affair with at one point due to feeling lonely, though he ended it himself out of guilt.
Mentioning her name can cause Trip to eject the player from the house. This depends on a number of things mainly being Trip's mood, if he is happy (like when the player first arrives, or he is fixing the drinks) he may attempt to laugh it off saying he doesn't know any Maria. But, if he is in a bad mood (for example if the player has been annoying him, or he is fighting with Grace) he will eject the player from the house.