It was mentioned that she was a daughter-in-law, so it seems that she's the wife of the ML's brother, meaning she is from another noble family and just married into the Ducal family.
oh thanks for the fact check (づ￣ ³￣)づ
but still if she is marrying into a family that is involved with the royal family wouldn't she still need a lot of training or is it a age problem?
Yep, she's definitely lacking on that part, I agree. It's never justifiable to blame others cuz you feel insecure about your own shortcomings. I just felt the need to clarify about her relationship to the Ducal family, since she's ultimately just the sister-in-law and not the biological sister of ML.
And not only that but also she was a daughter-in-law imposed by the royal family to the first son. Because of the whole "obedience" situation, that's what the Duchess what saying to MC when she was trying to convince her to not enter the family through marriage at least.
if you haven't learned royal etiquette to potentially be a spouse that on you for dropping the ball
and it seemed like your mom was willing to train you as well(╯°Д °)╯╧╧