While I feel it's fair to think that the Guardians intend to take her soul or demand she becomes one of them, I think they're simply gonna keep her on their watch for now: when they left the hospital plenty of demons/ghosts started coming out of the building, like they sensed her presence. She seems to attract them somehow, so it seems logical the Guardians who helped her would be interested in her, she's probably disrupting some kind of balance between the ghost and human world.
Also, I'm happy this arc involving Zen is "over", couldn't really care about this character. Give me more Hana and Julia.