According to the latest research she presents in her book, love is not so much a noun but rather a verb. It is something that emerges in micro-moments of interactions between living beings, when they share a positive emotion, resonate with it in synchrony and build on it to deeply care about each other.
In other words, love is in-between.
This view mirrors the stance of Solution-Focused practitioners when we say that solutions and change and the future all emerge in-between, in the space of dialogue and interaction, rather than being determined by inner drives or outer social pressures.
Seeing how SF and current Positive Psychology thought are somehow converging on this interactional view was quite interesting to behold.