This page is a pretty interesting look into Fiona's mindset right now. Killing someone takes a lot, and it's not like she's pulling a trigger or telling someone else to do it, she's shoving a sword into her chest. I own swords, I've been stabbed in the leg with a sword, I've dealt with sword wounds. They don't just slide in gracefully like in a movie, that is a seriously forceful blow to pierce someone's chest. I'd love to see into Fi's mind.
Is she still feeling malice, or is this the mercy killing Clandy asked of her? What are the repercussions of this on Fiona mentally and emotionally? Now that the deed is done, does it really matter? Does Sadako even deserve a mercy killing? She sent her conscience away, she brought all this on herself. Still, a death is a death. Murder, assisted suicide, execution, it's still got to weigh on the heart.