I'm assuming you are interviewing her for a written article, rather than conducting a radio or TV interview.
Michael Parkinson, the doyen of British chat show hosts, who worked for years in print journalism says that he has always got more interesting answers by keeping his mouth shut and listening and raising his eyebrow occasionally.
Short sharp questions such as "Why?", or "How?" are infinitely preferable to asking things such as "You obviously must have been very upset - were you?".
That boils down to always ask open rather than closed questions unless you are fact checking.
"Who do you think is the most underrated author?" is quite good for writers.
Added: Sorry. This won't apply to you if you are having a third interview with the same author, but just in case any tyro journalists are reading this DO YOUR BACKGROUND RESEARCH. There is nothing less conducive to 'giving good interview' than being faced by somebody who hasn't bothered to even read the press release, never mind the book.