[quote=@Silvan Haven]
Somehow I feel like that would be a bit more than just gradually kill the Grimm. Seems like it would be more immediate.
[/quote]

I was thinking the same. But the purification could be be stopped just shy of the last 'drop' of darkness. That would achieve the desired effect. She would definitely prefer to just kill a Grimm, but I also think there would be those that insist she use the 'turning' ability as much as possible.