In a rather comforting way (if that is the right word) I hope the mother did kill Maddie in a weird way. At least the poor child would not have suffered at the hands of some sexual molester.
Obviously, I hope the child is found safe and well, but if fate has it that she has demised, then a quick kill from the hands of a misguided or possible pscychotic parent is surely better than her being locked and abused by a nonce.
Whatever the outcome, justice will be served one day.
Personally, I do not think the mother is involved. I know it is a very shallow thing to say, but she looks quite sane, and indeed pretty. Rose West, Maxine Carr, Myra Hindley on the other hand all looked a bit odd.