Did Snape really love Lily, or was it just an obsession? Did Lily love him as more than just a friend when they grew up to be adults, or was it just Snape?
An intelligent man once said that love is a "never-ending circle." One gives their love to another, initiating the first half of the circle. The receiver then gives back to the lover, completing the circle, over and over.
Lily and Snape were friends who grew up together, and would eventually part ways, but nothing ever indicated that Lily ever stopped caring for Snape, just that Lily stopped talking to him.
Come to think of it: everybody in a relationship has had a fight/falling out. That's normal.
Even if Lily’s romantic path became one with James Potter doesn’t mean her feelings for Severus faded away.
Obsessions, on the other hand, are often short-termed. And we all know that Severus loved Lily even after her death, and put his life on constant danger for her son.
So was Snape's love obsessive love?