Sentence:  “In that case, sir,” she rejoined, “as my kinsman's politeness seems to be still slumbering, you will permit me (though I suppose it is highly improper) to stand <WSD>mistress of ceremonies</WSD>, and to present to you young Squire Thorncliff Osbaldistone, your cousin ...” 
Meaning of the word marked with <WSD> tags:  A woman who acts as a host at a formal event.