The sitter's identification is traditional. Geneviève Savalette, Marquise de Gléon (about 1732 - 1795), was a writer and amateur actress. The dress and hair-style date to about 1760. The traditional attribution to Greuze is a possibility but a firm attribution is problematic due to damage on the face and neck.
The National Gallery, Trafalgar Square, London WC2N 5DN