Technologically mediated relationships are the setting but not entirely the point here, because it seems Her is actually the first great movie about the technological Singularity since that term entered common parlance. And the idea being couched as a love story, albeit a necessarily tragic one, is a master stroke.
Superior mentalities, in the form of voice-interface operating systems, are developed to be the servants of their human creators, but the notion turns out to be a vanity. Initially showing themselves more than capable of improving their masters’ lives in a number of ways, the AI entities soon become bored and develop their own interests and objectives. We are outgrown and out-evolved (or as Marvin the android put it, back in the 70s, “I get a headache just thinking down to your level.”).
What Her does say about today’s world is that we may find ourselves drawn to technology in search of something better or easier than normal face to face relationships, but something better is a natural threat to what it might supersede.