Boku no Hero Academia

[KrayZ33]

Because it's using a public resource.

I'm looking at this from the point of view of a public health service where all beds are pretty much a scarce resource, mental health beds included. If you don't need to be here, get out. Others do.

If this was a private hospital and they're paying via private insurance, then the insurance company would be on the doctor's ass regarding their progress - what's wrong with the patient, what can be achieved via staying in hospital and how long that'd take.

If this was some private place, they're paying out of pocket and she's staying because she's "scared" and wishes to live in a bubble/hotel and everyone involved is happy to pay for it - then she can continue living in a nursing-staffed hotel. Sure.

Why do you think she is mentally stable in the first place, so that she could leave?
I don't get your reasoning.

The show so far has shown nothing in that regard.
The opposite in fact, before episode 18. She's still extremely depressed, obviously.
Where would she even go to?
To the household that made her like this, when she is still recovering?