Of all this I might have been mistress.
Explanation:
Lizzie about Pemberley-Mr. Darcy's house.
Of all this I might have been mistress.
— Is this the proud Darcy you told us of? He is all ease and friendliness. No false dignity at all!
— I' m as astonished as you are. I can't imagine what has affected this transfotmation.
— Can you not?