It was more like an alarming sign for her.
"Why would Duncan know where my mother is? Right?" She was almost sweating for the fact that if he would have ever know it, then that means that he knew that the person in front of him is not Rachel but Regina.
And that would indeed have become a very serious problem for Duncan was known to be the one with sour mood most of the time. He also had a bad habit of blaming his mistakes and misfortunes on other, so knowing that he was getting deceived by a count, he would have made sure to kill everyone of the D'Azure family.
Regina calmed down.
She let go of Duncan's collar and stepped back. "I apologize your majesty, it was ... in a heat of moment. I apologize for this misbehavior." She said with a genuine tone for apology bowing down to the king.
"Hmm? So I should just forgive your act? Just like this?" He asked in a sarcastic tone. Regina immediately regretted apologizing to him.