There are few bugs at boss fight...

First is: After defeating her, charming her before speaking to the book will cause a glitch where you cannot continue the animation

second: Loading the last checkpoint during the fight might cause few of these problems: 1) arena will not unlock as the boss is still there. 
2) Camera gets locked at the middle of the map not following the player 

Hope this helps. It is a great game btw, but these glitches made me ragequit :D