There's much we don't know about this mechanism, though.

but her case seems to be beyond exceptional.

Since time immemorial, creatures without physical bodies have often obtained them by possessing humans, animals, or abandoned remains...

But though her basic nature beyond her appearance was unchanged, she was able to recycle that outside sustenance to complete her tsukumogami transformation.

As a perfectly preserved corpse turned into a tsukumogami, she required no outside sustenance to bind her to the land of the living.