Mrs. James Douglas
Maiden name Mackay. Married to James Douglas (a Capt. of the Guard in 1763).
Life with Boswell:
Boswell met her on January 3rd, 1763 at the Gould's. He didn't recognize her at first, but later that day admitted to having had a crush on her when he was 13 years old and recuperating from disease at Moffat. Boswell also reports being with a Mrs. Douglas at the Goulds' on January 8, and at Mrs. Douglas' with the Goulds on January 15, 1763, but Pottle identifies this Mrs. Douglas as the wife of Andrew Douglas. They may of course have access to papers asserting for certain which of the Mrs. Douglas's he wrote about, but from the journal itself I don't see any clear identification.