Boring fact: The underlying theme of the movie Her is actually divorce and the destructive impact it has on people, the futuristic AI stuff is just for stuffing!
The overall theme of Her was human relationships. It was not about AI and not just about divorce in particular.The AI was just a plot device to include a bodyless person into the equation. Watch it again with this in mind and you will see what I mean.
The universal theme of Her was the set of harmonics that define what is something and the thresholds, boundaries, windows onto what is not thatthing but someotherthing, even if the thing perceived is a mirror, not just about human relationships in particular. The relationship was just a plot device to make a work of deep philosophy into a marketable romantic comedy.