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.
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 °)╯╧╧