Irina was not able to do certain things not because she didn't try, as the user to which I replied suggested. She tried very hard and she did improve a lot. She just couldn't be in the same league as Kwan, in that particular sector.
Also, do not forget that not all skaters are balletic, or "classical", if you prefer. No matter the lines there is also the style we should consider.
As for specific body types about ballerinas for example here is an interesting docu. https://www.youtube.com/watch?v=1zCTdkJ3kjo