CN is an academic AA - great student. Dad went to Princeton. She knew she would not win at Duke. Coach and team were not as focused and driven to be the best as she was. It is that simple. She did not want her last 2 years to slip away without an opportunity to win a NC and be the best player she could be. Have to give her credit.
You have no idea why she left as it has never been publicly stated by either Duke or CN. Maybe the Duke coach told her not to go to goal in the last 30 seconds when they’re up by 10? BC doesn’t seem to care as she did it often last year.