> kept almost deliberately vague
I think it's a mix of lawyer advice and a disavowal of Dr. Mao as her advisor -- a way to maintain some dignity. The member of the dissertation committee who is most likely to be "impossible" to remove is the chair. More evidence for the roles: "I told Dr. Hortense in this November email that I was worried about my ability to pass my defense, especially if Dr. Mao was not going to read it prior to sending it out to the entire committee."
Yes, I now agree with you and upvotinglurker. That also explains the mystery, and the hidden horror: her advisor plagiarized her.
She also mentioned that she would have been elated if Dr. Mao had just credited her in a footnote when he published her work. I imagine that this is shitty, but common in student-adviser relationships.
She does seem to state that her defense was conducted by three people - Dr. Mao, Dr. Hortense (who she did "go to" and got an unhelpful response), and "The third person in the room, another professor on my committee" who appeared surprised by the proceedings.