There's a lot of unseen practice and grinding not shown. And Inori is inherently gifted, although shackled by her personality.
She's in the genius category that can learn level 10 tricks at level 1 just but watching them once, but also can still mess level one tricks.
I'm not that surprised. And she needs to catch up to her age group fast and even grow faster than that.
Remember that B level girl, that's who she needs to compete with and beat for her olympian dreams, because that's only Japan, the world stage will bring even thougher athletes.