I mean, there no way for them to really hide it... in the novel i was skeptical as to whether its sylphy or not, but with art and voice acting its impossible
:( fair
I havent watched the episode but I feel like the approach to knowing it's Sylph while Rudeus has 0 clue creates tension and suspense and it'll feel so much better when he actually finds out it's her, but like the other guy said it's way to obvious considering voice acting, and it's still pretty obvious if your the reader.
It isn't impossible. They changed her character design from the Novels. If you look at the illustrations in the novels you'll notice she looks way more boyish and you wouldn't really recognize her that well. Also in regards of the voice actor - they could've just chosen a different one and not shown Sylphy speaking with that voice last season.