@calibus the way I read it was that she killed herself before anything could happen. When Lily absorbed her body, some "trace" of her soul remained. Presumably Miho liked him even though nothing ever developed between them, so Lily answered Miho's dying regret, while giving into her own desires as a servant, and forced herself on him. Afterwards, that remaining part of Miho vanished.
I might have misread things. Certainly wouldn't have been the first time. But I like my interpretation which gives the girl some closure and makes her death a little less tragic. If you really want to gripe, consider that she abandoned her junior, Katou, to that horrible fate. Armed with a knife, perhaps the two might have been able to fight back.