Question

Both of them got a different poison. Peneloppe prepared a poison "just in case" but didnt actually use it. The sister used her maid to put poison in her drink so shed look like a victim and put the blame on Peneloppe. But peneloppe saw the sisters cup was poisoned thanks to the necklace and decided to drink the poison so she wouldnt get accused

Part of the story was that yvonne drank the poison and penelope got blamed, yvonne planned it herself because penelope wasnt a bitch