A Macbeth Question...?

No, the witches never speak to Lady Macbeth, and they never promise her anything...except indirectly. We know from Lady M.'s first appearance in the play that Macbeth sent her a letter containing the particulars of his first encounter with the witches, and their prophecy. So, Lady M. knows that Macbeth has been told that he'll be king, and, obviously, she is instrumental in keeping her husband focused on the plot to murder Duncan.