Responses
She is not, she is single. i think she just said that to get the point across.
Spoiler:
She becomes duke's wife and mc's mom ε=ε=(ノ≧∇≦)ノ
Me when I lie
No I think it's a mistranslation, she is supposed to say "YOU are married", probably. Non-official translations always have problems with pronouns (I guess it's because in korean, pronouns are implicite just like japanese maybe ?)
oh