During his stay in Berlin in 1764, Boswell lived in the house of Karl David Kircheisen, the president of the Berlin city council.
Life with Boswell:
Boswell met Sarah, often referred to as Sally, and her husband at Stewart's in Rotterdam in 1763 and 1764. On January 11, 1764, he played cards with the two for 7 hours, and afterwards referred (in his memorandum) to Sarah as "erst maid and w--re".
A son was born to a John Mollison and Sarah Mills at Rotterdam in June, 1766. This is my reason for giving her full name as Sarah Mills, although her last name didn't appear in Boswell in Holland 1763-64.