Correct me if I'm wrong but I believe the Witch was bluffing as a Slayer? If yes then it's not a bug per say but a rule that is a bit confusing. When a Lying Slayer (Any Evil except Puppet Slayer, or a Corrupted Slayer) tries to kill someone it will automatically say "x is not Evil" no matter if it's true or not. Why? Because it counts in the code as Slayer's ability not working (the same way a Lying Alchemist cannot cure). In the future, I recommend imagining that, instead, the slayer says "I could not kill x" (which, I believe, is what the Slayer says in the steam version) and remember that a Lying Slayer is not so much a lier as it is a character that just does not work. As for the Pooka, it is in fact lying because, to Pooka, The Witch is a lier.
Hope this helps!