Hey there
For a proof to be accepted, it means it has to be 100% certain, with no other possibility . The problem is finding what your Autumn leaf cats are hiding as cats can hide for generations. You would need to prove that Abraia's four different grandparents were all pure AUtumn leaf.
But what you can do if you want to help make a lower range, is breed your new baby to an extremely recessive eye like faded flower and see if you can find what is hiding under Ardala
You would have four possibilities for the kittens
If the second generation babies showed anything dominant to faded flower, but not Mountain magic, that would be a proof that mountain magic is dominant to that hider and give a bottom range.
As julinah got the original against brushed steel, this would definitely be worth trying