This Luise was born in 1756, but this is a 1760s coiffure. Coiffures became curly in the 1760s and then swelled upwards. This occurred later in German regions than in some other places so maybe this from the early 1770s or this is not the Luise born in 1776.
From Wikimedia.
This dress does not appear to have a separate stomacher. The stomacher area is set off by overlaid gold bands.
Keywords: Malcote, Prinzessin Luise von Saxe-Gotha-Altenburg, Princess Louise of Saxe-Gotha-Altenburg, Prinzessin von Sachsen-Gotha-Altenburg, Herzogin zu Mecklenburg, Luise von Sachsen-Gotha-Roda, Wettin family, Mecklenburg family, Princess, Duchess, German, curly coiffure, hair jewelry, girandole earrings, jeweled choker neck band, fitted bodice, off shoulder scoop neckline, brooch, elbow length close sleeves, gold lace forward-back flared engageantes, lace engageantes, vee waistline, full skirt, robes, clasps