Dear Vanessa,
Though cliff-hangers and quite in trend these days of sequel writing, I personally feel that an ending of a book cannot be incompatible with the character.
NEAS has a heroine that while never wanting to be a hero does not hold back when the right thing to do is clear to her. Is it how you see her too? Because if that is the case, no amount of surprise or heartbreak would break her for long and thus the current ending of the book cannot be a proper ending no matter how satisfactory it might feel.
If the point is that nobody is perfect that is cool. But nobody is imperfect in what is his/ her core trait. There are so many things in life one can screw up. And usually you fail what you strive to manage not what spills out of your soul without you wanting too.
So, basically what I am saying is that -while a great piece of writing - NEAS with that ending is not an actual book. At best it might be a part I of something.
I like your writing and I like some darkness in the mood of a book. While your world is dark enough, the disappointment from the heroine feels forced. One should not strive to lead a character where the character does not wish to go, and certainly one should not sentence a character to a permanent state of being out of character. The world, yours and the one we share alike, is hard and unfair enough as it is. Does not need us to forcefully twist it that way any more than it already is.
With great hopes for you and a full book of yours,
Orin
the grumpy old dwarf.