Ivy didn’t approach Dresden at either event, guilt over Thomas?
The Oblivion War is to remove certain rituals from human and other knowledge, including those which summon Outsiders, someone whistled in the Corner Hounds, someone among the Svartalves? Maybe Austri was the target all along? Or Etri or Evanna.
The archive will know every recorded fact about White Court Vampires, their origin, how to defeat their hunger, how to stop a Whamp baby feeding on the mother, and how to ensure a whamp reproduces. A pregnancy test, sonargram etc are both recorded information, Ivy would know because of her intellectus without bugging Thomas and Justine, when even Lara doesn’t know, which explains the absence of bugs or magic in Thomas Flat, which Harry took a lot of time establishing.