To be fair with how her story plays out and how she changes when you aren't romancing her I had a slight feeling she would be like that at the end, but it would have been nice if it was more of a mystery.
Problem is it's specific dialogue in her act 2 romance and act 3 romance scenes that was spoiled too, dialogue that would seem really emotional if you experience it blind. Probably still is to be honest even after seeing what she says before I see it in game because it's one thing to see what she says but another entirely to experience it firsthand.
In my first playthrough I very much gravitated towards Karlach. And when I was in Act 2, Gale, Astarion and Karlachs endings were all spoiled for me before I even got to Act 3, and tbf especially Karlachs quest, they still got to me even though I knew what would happen with her engine.