The thing is, I'm almost done the book by the time this happens. The woman in question is a supporting character in the book, with not that many scenes. Her being confronted by her previous master - who is my book's main vilian, but for different reasons - was a plot twist I added in at very nearly the last few minutes of the book. I plan on expanding on her story and following where this plot twist goes in a later book. I do admit that there is very little in the way of foreshadowing her trauma leading up to the confrontation, but that is what I think adds to the mystery of it all.
Basically the woman (Isabella) is a friend the hero's - the main male protagonist - and very close to end of the book, she is searching a mansion where the hero has gone earlier, trying to help him. The antagonist (Edward) of the whole book is on his way of the final escape, when he sees Isabella,recognizes her, and uses his power over her to aid in his escape, taking her along with him. Isabella *could* fight him off, but because of her past history with him and the sudden shock of him being there and holding a gun to her throat (which my character could defend against had she the will do to so) throws her into a trigger where she becomes helpless to refuse him, like she was trained do as a child and teen while being a slave to him.
The whole event is supposed to act as a suprise and an almost-to-end final plot twist that will lead into further books and stories.