She doesn't actually have anything close to enough information to figure this out (neither do we), though it can also be argued that she's not smart enough to realize more information is necessary?
Either way, she's being too hard on herself.
IN ANY CASE... I'm not ready to say how canon the whole of this storyline is.
I AM ready to say, however, that anything we learn about Jay's backstory IS canon.
This somehow reminds her of her first encounter with magic, she does have the spell she's describing, and it is the first spell she ever learned.
She is also canonically not smart enough to figure this out, but again, she doesn't have enough information, so it's not really a matter of smarts.