Skis are like the only place. Weirdly, I still do poles in inches! Hate cm for poles.
As to the girl’s ski length, you’re starting to get into a zone where length can be a preference based on ski type. I.e., (Latin is metric, no??), she could be 6ft…er 183cm tall and a 155-57 could be perfect in the right ski.
That’s probably a year or so of experience away.
Here’s an example of a ski too short. I skied with a kid and his mom the other day. He is 4, is on 70cm skis. Ok, that sounds just fine, but in reality, he completely out skis the skis. He goes shockingly fast, fully parallel. It was actually really scary seeing him come down at first, I got out of the way. But he reliably shuts things down, and the skis are so short they just burrow in sideways and stop.
At his speed, in the soft spring snow, the skis don’t have enough length to actually turn him in a round arc. I would put him on 90 or even 100cm skis right away. He’d have to learn to turn them, or what happens when you turn them. If he skied the exact same way, he’d shoot off into the trees. I doubt it would take long to adjust though.
Ski design doesn’t have to concern you much at this point. Just know that longitudinal stiffness, how stiff a ski is when you flex it, is not the only stiffness that matters. There’s torsional stiffness, twisting along the width. Racing skis and advanced skis are torsionally stiff, you put them on edge on hard snow and they hold. Beginner skis are softer torsionally, so they release that edge very easily, and don’t grab and hang on.
