But doesn't she mention the DSM criteria in the beginning of the book? Self-injury, suicidal ideation, problems with interpersonal relationships and emotional regulation, and risky behavior (granted she was a teenager in the late 1960s so you can give 'er this one -- sex drugs and rock 'n roll) -- isn't that still under the DSM "definition"? An aside, but she also had visual hallucinations.
I may be completely speaking out of ignorance, so please school me if I'm totally wrong.
What I got out of the book was that she didn't fit society's expectations of what she was "supposed to" do (similar to the crisis that Sylvia Plath's character in the Bell Jar had), but it was really the suicide attempt that landed her in the hospital.
Also, Hershi, I think part of what she's trying to say is that she's not sure either.