Assuming Wanda DID find the Arkenpliers, I can guess as to why she would be better attuned to it.
Remember that the Arkenpiers are effective againts Uncroaked. This suggests that they are associated with Croakamancy. Ansom wasn't a caster, but Wanda is, and a Croakamancer at that. She is especially suited to using it.
Maybe suited enough to Uncroak every unit killed in the eruption? :evil2:
Edit: As for what Ansom took from Wanda... I think Wanda was/is in love with Jillian. Jillian's loyalty was torn between the two of them, but when the spell broke, not only did it fry Wanda's brain, but it was effectively a rejection of her feelings. Hell hath no fury like a woman scorned, and there's a thin line between love and Hate.
Another thing... judging by the fact that she received sushi for her daily meal and that some of her clothes seem to be of an Eastern bent, I think that Wanda may have been a native of Faq at some point, similar to Jack the Foolamancer. That would explain why Wand a was so angry at Jillian for siding with Ansom. They could have had a significant history before the war even began... makes you wonder.