
I'm stupid who has the poison? I feel like Yvonne has it, which is gonna make pen look bad is she drinks it, cause pen wants to die.

That's right. Yvonne's maid (who is brainwashed) poisoned the glass. She eants to frame Penny. If you look you can see the marks that someone already drank from the glass, and that's why Penny said they were switched. So she can get poisoned instead, to not be framed, and, well, to die. Since that was her plan from the start
just finished reading this and man the emptiness i feel knowing that other manga don't compare when it comes to this well written story and the multi faceted villains