Here it is folks. Spoiler alert btw.
ヾ(❀╹◡╹)ノ~
So Penelope don’t want the birthday banquet because she thinks it’s inappropriate at the moment because they are still in the process of checking whether Yvonne it the real the daughter or not. But the Duke is so insistent in pushing through the bday banquet, and he promised to Penelope that he will not let Yvonne go to the party.
During the party, Yvonne still went to the banquet with the help of Derick. And that was the last straw for Penelope to go through her plans.
Penelope actually ask her maid in this last chapter to purchase a poison so that she could poison herself. But she will do it after the party.
Now going back to the party going on. It is tradition to drink wine from a cup that looks like a challis as a sign of adulthood. And during this time, Yvonne will also do the tradition(forgot how she orchestrated it but in short Yvonne and Penelope will drink from 2 challis). The Challis that was prepared for Yvonne actually has poison, Yvonne wants to frame Penelope but to her Surprise Penelope switch their cup and drink the wine with poison.
Everyone is in shock and panic because Penelope suddenly faints. While Yvonne is the suspect, Derick of coarse takes her side.
To make share the events to come after the banquet, here it is:
1. Penelope’s gone into a coma
2. Callisto is panicking and does not leave Penelope’s side. He finally realize that Penelope wants to leave the duke’s mansion.
3. The maid says that the Princess actually plan this and wants to take her life. Which she did prepare to take her life but this was not is because this one is from Yvonnes poison.
4. Penelope wakes up using an antidote.
Then after Penelope wakes up is the final Arc. I’ll spoil this later, only if you want me too

I’ve the novel for this and we’re about to go to the exciting part. Who wants spoiler??!!!