No doubt they've realized they can't separate him from his delusions. And yeah, he's mostly harmless, but it's pretty retarded for a supposed social worker to pretend to be Leaf and agree to marry him.
It's easy now, but as with most fantasies, the amount of effort to keep feeding into it and addressing any contingency that might shatter his beliefs is futile. It works with old demented patients because they'll probably die soon anyway. Not so with PL; pretending to be Leaf is going to be a life-long job. It seems extremely foolish and unprofessional.
You're implying she's fine with this client of hers, who has a penchant for posting his every thought online, literally telling people that they are actually married, and holding herself accountable for his feelings in a capacity that far over-reaches what an actual professional should have. Romantic interest is one of the big no-no's for carers of vulnerable people, pretend or not.
What are they going to do when her case-load changes or she moves to work at a different facility? Is she going to be forever beholden to a single sperg for the rest of his life, lest he go wild and start screeching that his real-life rules marriage is being torn apart?