In the beginning of Chapter 10, Leanne is unaware of the Crank Seminary incident's anniversary and didn't know that it was the day Vashyron and Zephyr met. But considering she's lived with them for over a year (counting from Christmas), shouldn't she have experienced this once before already?
Adding to that, a lot of dialogue (in Ch 13 and 14) makes it sound like it really has been only a year since she joined the hunters. So when the game's opening scene says "A year and a few months later" does it count from Vashyron and Zephyr's first meeting or Zephyr and Leanne's? The game probably makes more sense with the former.
Why would it make sense in the case of the former if the words "A year and a few months later" appear after Zephyr and Leanne's meeting? And it's clear that said meeting was Leanne's first glimpse of any place other than Chandelier — heck, anywhere other than the laboratory where only Juris and probably Rowen or Sullivan could interact with her. I doubt any of them thought it necessary to let her know anything about the rest of Basel. As for likely having witnessed Zephyr's ritual visit to the seminary once before, maybe she wasn't yet employed as a hunter and didn't think it was any of her business.
What was Leanne doing that year between her release from the lab and her suicide attempt anyway?