Accurately describing the state of opponnents' card, especially in 3P+ games, runs into space restrictions fast
What you saw on Lord Rat's turn (that you controlled) initially was this:
Notice that the info bar for Revenge Witch has a slighly yellow hue. That means that what you see on the top of the screen are Revenge Witch's card (in hand, discard pile etc.). Usually the next turn's player is chosen for that. Since Ingix (in my reload) was the last player in turn order, Revenge Witch had already discarded for the Margrave, so she only had 3 cards in hand.
If you click on any of the other opponents' info bars, you get to see what there cards look like. If I click on Ingix' bar, the display changes at the top:
Now you see Ingix' info bar in yellow and their hand cards face up (since they are yours) and they have the typical yellowish border indicating they can be discarded. And that is where you select them from for discarding.