She is probably the daughter of Anne Molesworth.
Thanks to William Molesworth for identifying the location. From Wikimedia.
Louisa Anna has a high coiffure decorated with a draped ribbon over un-powdered hair in this Hamilton portrait. She also wears a veil.
Keywords: Hamilton, Louisa Anna Molesworth, Molesworth family, British, high straight coiffure, ribbon headdress, veil, chemise, modesty piece, scoop neckline, bodice