This is the "Doña Isabel de Porcel" painted in the Spanish style. The sitter, Doña Isabel de Porcel, wears an elaborate lace shawl and headdress, known as amantilla, which is masterfully conveyed by the artist's use of zigzag patterns. She was a woman from the lower classes whose fashion sense influenced royalty and aristocracy during the late 18th and early 19th centuries.
Goya exhibited a portrait of Doña Isabel at the Royal Academy of Fine Arts in Madrid in 1805, but it seems unlikely that this is one of his works due to some recently raised doubts. When an X-ray image was made of this painting, another portrait was found underneath - you can see the dark curve of a man's eyebrow on Doña Isabel’s chin and the stripes of his jacket through her right sleeve.
The artist reused canvases during periods of political upheaval when materials were scarce, which suggests that this painting might have been created soon after the one underneath. Despite its intricate details and long-held status as one of Goya's best works, its authenticity has come into question in recent years.
Doña Isabel de Porcel hangs in The National Gallery on Trafalgar Square, London — free to enter. Point your phone at any artwork there and audioguide.london plays a free audio guide in six languages — no app download needed.