You know your DD, the best in the world.
Ime, it’s not a revolving door to inpatients, unless they have psychosis. From what DD says, people get taken there under section, because they have been acting out in a public place for instance. The HCPs look at the meds. As an inpatient, they live in a routine - they have to take their meds, they get three meals a day, they can play table tennis, do quizzes, etc and if it’s somewhere reasonable, they can talk to the other patients awake, and the staff 24/7. They come out of the psychotic episode and get discharged. They go home - don’t bother taking the meds, eating and drinking properly, or taking care of personal hygiene. They end up in another psychotic episode and being sectioned again.
DD was admitted twice for being very suicidal, this after 50 plus instances of suicidal behaviour. After the second time, even when a mental HCP assessed her in A & E as needing admission, the gatekeeping psychiatrist refused.
Ime, psychiatrist’s thinking revolves around drugs, and waits for any other kind of treatment are 2 - 3 years long. I’d say, for people who are not in psychosis, being admitted here is about as easy as getting an EHCP for an expensive residential school!