Like I said before, the trick is very easy as it only involve the door and the key. As for the key evidence of her own undoing, here's a hint; it boils down on making a simple mistake on certain word mix up. You can see the clue on the previous chapter. And as I said at the start of this case, this case is the complete opposite of the butterfly of death murder case. Just wait for the reveal. here comes the bird rowas