I feel bad for Igarashi. She's made some bad decisions, and her trying to justify her actions to herself shows that she still has a long way to go, but at the same time all of her poor decisions and actions come from a fundamentally human place, not just the sort of generically evil rival I would have expected. I also really like that she respectfully bowed out when Nanoha stepped up to the plate, instead of trying to stick around and put her own feelings ahead of their relationship. Honestly, that she still has so far to go, makes me really want a future appearance or a spinoff or something, her journey would be a really compelling one to see.