with her being able to do dual-rotation jumps with so little practice

My understanding is that she had been practicing hard all along and perfected the fundamentals, making it possible to pick up advanced techniques in a short duration. We just never got to see her practice on her own.

This is me bragging thinly-disguised as an example, but I can relate to this with first hand experience. I went from being complete beginner with no experience at skiing to do red runs regularly in a matter of days (to be specific, in about 2 weeks in total) which is considered kinda fast from what I’ve heard. One of my instructors pointed that because I did not pick up any bad habits, I never had to unlearn bad habits during lessons. Instead, I could simply pick up new techniques each time, building upon whatever I have learnt before.

IMO Inori is in the same boat as I was, so I found it believable.

For context, ski slope difficulty levels go something like this: learner -> green -> blue -> red -> black -> off-piste / free-style