I'm not sure it's that clear cut. Harrowhark's power wasn't foolproof, like if someone else had used it. There's a margin for error, and unfortunately we don't know where that margin lies. Both she and I apparently had the same assumptions about it, and we were wrong.

Which would mean someone still did kill her, and is running around just fine. I'm not a fan that we keep falling back on this moral dilemma of "do you judge people for things they might have but didn't do", but this one feels a little different.

Probably why, if all this theorising is correct, it was accepted as a correct answer.