Obviously Siegfried talking about Fafnir

A classic French tale.

That girl must be a lovely girl, beauty, and, full of determination. I wonder who she is 🤔

Sounds like Charlotte Corday.

Let's look at what french servants we have that kill people.

(Everyone except Marie)

Who of them need to plan to kill people.

(Gilles Caster and Charlotte Corday)

The conclusion, thank you Charlotte Corday for killing him. Thanks to you my brother couldn't remember that difficult name of the guy that succeeded him. Marat would've been an easy name to remember in history class.

The clue started with She said so obviously the answer should be a girl.

The killing needed a plan, which means that the killing was something fishy, aka Assassination.

French, obviously, French.

So yep answer was Corday. Funny that one of the contestants answered Jeanne.

Well given the way the question is phrased, the whole "not killing a man but a beast devouring the french people". You could take that to mean figuratively a war was killing the french people and Jeanne stopped the beast of war that was killing hundreds of people.