After completing the requirements, they then complete two or more years of independent research and complete a book-length summary of their findings that, on approval by their dissertation committee, will grant them the doctorate.
I had already obtained a masters degree from one school when I enrolled in a doctoral program at a different school. I was surprised when the head of the department said that the MS was a consolation prize for those who couldn't finish a doctorate. It certainly wasn't such at the place where I earned one.
However, once I successfully defended my dissertation, I was officially a PhD, and could call myself Dr. I didn't have to wait until I'd gone through the ceremonial formality of walking across the stage. At some schools, I've since learned, it's that formality that counts. You can't call yourself Dr. until you actually have the diploma in hand.
I've read varying stories about Ms. O'Bagy: that she had defended her dissertation; that she was enrolled in a doctoral program but hadn't completed her dissertation; that she wasn't even registered as a student. I don't know what the truth is.