Theresa Natalia (1728-78) is wearing the blue ribbon of the Order of Gandersheim, the cross of St Catherine, another cross and a blue jewelled crucifix at her waist. She was one of the daughters of Albrecht, Duke of Brunswick-Wolfenbüttel. In 1767, she became Abbess of Gandersheim, Germany, a community of unmarried daughters from noble families, who were not under religious vows.

The inscription on the back of the miniature suggests this is a portrait of Sophia Antonia, a sister of Theresa Natalia, but it would be unlikely that the insignia of the abbey of Gandersheim would be worn by anyone who was not a member of the order, and comparison of known portraits of Sophia are different from this miniature.
In 1767, George III bought 'twenty or more Miniature or colour'd drawings copied from the German of the House of Brunswick' and this miniature was among them. The identity of the artist is unknown.

Inscribed on the paper back in pencil: Braunschweig Sophie Antoinette Hersogin zu Sachsen-Coburg.