Well, she can't play smart. She's an illegitimate child. That's a status even lower than servants. She was always treated harshly and she is smart to think ml's attention might end after he gets bored from his reputation instead of swooning for him and becoming annoying. She chooses her words and actions as that's how she survived all her life.
Yeah maybe thats why i said cause im getting used to read manhwa which the fl straight forward.. and maybe sly like a fox can take advantage when they know the duke is like a puppy to them even tho maybe she think its for a while like nt permanent she can take advantage to tht (=・ω・=) but yeah this like most of the story triangle love or the crown prince is the tyrant want someone else lover while the fl either endure it and the duke fighting for it ε=ε=(ノ≧∇≦)ノ

Maybe because im getting used to read fl who straight forwards and say what they want or what they don't like .. soo this fl gt on my nerves especially with the crown prince ( ̄∇ ̄") she is nt tht smart