“Live-In Maid,” Jorge Gaggero’s remarkably assured first film, examines the complicated relationship between Beba (Norma Aleandro) and Dora (Norma Argentina), an upper-class Buenos Aires woman and her longtime housekeeper. The two women share a roomy apartment, which Dora keeps in immaculate order while Beba primps and sighs like an opera diva with an audience of one, or the qu...