Maria Frederica van Reede
Daughter of Frederick William de Ginkell van Reede (d. 1747), 4th Earl of Athlone, and Louisa Isabella Hermelina van Wassenaar (d. 1756). Married (1769) to Count Sigismund Pieter Alexander von Heiden (1740-1806). Sister of Arend Willem van Reede and Frederick Christian Rhynhart de Ginkell, 5th Earl of Athlone.
Boswell was at Mademoiselle de Reede's on February 11, 1764. Despite her being only 15, she was probably the principal female representative of the van Reede family, her mother and aunt having died prior to this time. Boswell didn't describe Mademoiselle de Reede, but wrote that he himself was "gay, yet had dignity" when he met her.