I don't think the Duke can complain about the knight not reporting this to him. Though he'll certainly get angry, but really, this is mostly on his former cold attitude, which is definitely gonna go even harder from now on.
Case in point...Rich coming from the major workaholic telling her to take it easy.
When she talked about dizziness, my first thought was actually pregnancy, but I don't think that includes loss of appetite? Hmm. Probably overwork.