Actually, no. Chloe learning about Kanna being a dragon is 100% canon. Personally, I think they're just worried that she wouldn't be able to keep her mouth shut about how amazing her best friend is.
Haru Jigokumeguri, the main character of Ojojojo. She bought out Kobayashi's company at some point prior to the start of the series and has been both seen and mentioned multiple times, though as far as we can tell she has no idea that magic exists.