i feel like she wouldn't be in the puppet, just her ghost (think springlock scene), since she couldn't give life to the others, the children are stuck in WILLIAM'S happiest day which is all a ruse compared to the birthday party charlie throws in HER happiest day, and she probably doesn't want to move on unless the children are saved, also, henry's soul probably couldn't move on either since a portion of his remnant was in the ella doll lol