Maria was (like her colleague, Yvette, and her successor, Mimi) a young waitress at Cafe Rene and a prostitute for butter, sugar, chocolate, paraffin, gasoline, cigarettes, a bike, and that the fact that she would get shot if she did not. Maria was in love with and was having an affair with Rene, and wanted to elope with him. She was very poor, and was paid a very meager salary at Cafe Rene. It was implied that because of the amount of Germans in France that she could sexually entertain and could get money from, that they were not paid at all. In "Saville Row to the Rescue", it was revealed that she had previously been a prostitute in Paris and whistled like an owl, to attract attention. Maria was very brave and did help the Resistance. In "Pigeon Post" and "Flight of Fancy", Maria dressed up as a schoolboy, although she still wore suspenders and stockings. In "The Great Un-Escape", whilst in a prisoner-of-war camp, Maria disguised herself as a red cross parcel, but failed to put on enough stamps, and was thus sent "back" to Switzerland. Strangely and worriedly enough, Maria was never seen or heard from again.
Maria also had a habit of gargling the letter "R", thus causing her to spit on people near to her. She would become annoyed when they subsequently wiped themselves. This was a gag playing on the guttural R of the French language – Maria's speech was an extreme exaggeration of the stereotypical French pronunciation.