The scene where Firion is alone with the fake Hilda in her bedroom and all of a sudden everything turns pink, classical music (from Swan Lake) starts playing, and she says "Come to me..."
Firion's immediate reaction: *gulp*
Later on, when you run into the real Hilda, you can check to make sure she's the genuine article, at which point she asks if Firion's okay since he seems a bit flustered.