
I think that maybe you swapped people. Who killed herself was the duchess and not the queen, right?
If I understood correctly, Meraki's talking about the mother of princess Arien, that was acting suspect and talking with Cesare in the previous chapters.
If that's the case, I can give some spoilers from the novel, if you guys want.

Spoilers:
So, the queen is worried because the princess isn't well regarded by the nobility, since the queen used to be a slave in the East. I don't remember all the details very clearly because I read the novel a long time ago, but she makes a deal with Cesare to strengthen Arien’s position among the nobles.
In exchange, she helps him kidnap Ruby using some sort of black magic ritual or something like that.
The saddest part is that the ritual requires a sacrifice, so Cesare uses Ruby’s other brother, Enzo. At the time, he was visiting Ruby to check on her after everything that had happened. During this visit, that bitch Furiana starts falling for Enzo and begins to regret what she did to Ruby—but then he starts bleeding and dies in her arms.
In return, Ruby is sent to Cesare.
The final arc of the novel is about the mission to rescue Ruby from him.
But this is what happens in the novel—I'm not sure if the webtoon will follow the same ending.
WHAT DID THE QUEEN DO