Constance Mayer (Marie-Françoise-Constance Mayer-La Martinière) (March 9, 1775-May 26, 1821) was a French painter of portraits, allegorical subjects, miniatures, and genre works.
Biography on Wikipedia: https://en.wikipedia.org/wiki/Constance_Mayer

Self-Portrait with Artist’s Father by Constance Mayer
1801 / Oil on canvas / 89″x70 1/2″ / Wadsworth Atheneum Museum of Art, Hartford, CT

Constance Mayer on Artnet:
http://www.artnet.com/artists/constance-marie-fran%C3%A7oise-c-la-martini%C3%A8re-mayer/

Further reading:
https://www.findagrave.com/memorial/157540795/constance-mayer
Constance Mayer on French Ministry of Culture (Automatic translation by Reverso AI)
Constance Mayer-La Martinière (in German)