I've always suspected that she has paranoid schizophrenia, DID, or perhaps had post-partum pyschosis.
Back in the late 90s those were all seen as pretty scary illnesses - there were a lot of news stories, films etc about people who had committed horrific murders and similar whilst suffering from those particular illnesses, and they certainly weren't something that sweet, southern 'everygirl' Britney Spears could have been openly diagnosed with.
There's a lot more understanding around severe mental illness now, but even though we logically know that people with mental illness are a lot more likely to hurt themselves than ever hurt anyone else, I do think that a lot of people still have an initial, almost fear reaction to certain mental health issues. And despite all of the evidence that B is very ill, she and her team clearly don't want her labelled in that way. Which is obviously completely up to her, but I do think there would be some value in giving at least very basic details at this point. If only to stop the poor woman being constantly harassed by her 'fans'. This is no way to live, for anyone.