Any theories as to why Jadis is so weakened in the wood between the worlds, while she retains her strength on Earth and Narnia?

Digory and Polly, while initially sleepy and slightly amnesiatic, recover and seem to be unaffected on subsequent visits, but never weakened. However, Jadis is severely weakened and becomes ill immediately, but goes back to full strength on Earth and later in Narnia.

Any theories why it affected her differently? Was the wood actively or passively trying to hamper her?

I could potentially see the wood amplifying and directing people's characteristics back at them - Digory and Polly are just ordinary schoolchildren, so it doesn't do much to them, while Jadis is terribly evil, so it directs her negative energy back at her.