Her gift applies to all the Einherjar, and to date she hasn't shown any signs of having A Thing against Corwin. It's all about Anthy in her world. Everything she's done that sits outside her official duties to Asgard - the recall, hitting on Corwin, bringing Akio as her plus-one, attacking Anaximandra, murdering Clef - all of it is about svartelves in general, and Anthy in particular.

As far as I can tell, there's no motivation for her to cripple Asgard's defenders. In her mind, she's defending the purity of the Aesir from a race that is purely malicious and evil. (And yes, working with Akio would seem to be an irrational way of going about it. She hasn't been on the road to Rationalville for a while now, and that may have been the case before the Fallen Prince started whispering words in her ear.)

Peter Eng
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Insert humorous comment here.