I have a theory that she's faking her amnesia and somehow have a grudge on him. The grudge might be related to him dragging her to this alternate reality and choosing the girls instead of her, as far as she know.
I was thinking she's faking it, too! The way she took to Youta so easily, and the way she said that last line--it feels deliberate and very manipulative.
Since she mentioned there's something she doesn't want to remember, considering who the author is then we can guess that she doesn't want to remember being horribly tortured and whatever else they did to her in this world.