Alexandrina Robertson Harris (July 11, 1886–February 1978) was a Scottish-born American painter of portrait miniatures.
Biography on Wikipedia: https://en.wikipedia.org/wiki/Alexandrina_Robertson_Harris

Jacqueline Cochran by Alexandrina Robertson Harris
c.1950 / Watercolor on ivory / 3-1⁄2″x2-3⁄4″ / Smithsonian American Art Museum, DC

Alexandrina Robertson Harris on Pennsylvania Academy of Fine Arts

More links:
https://americanart.si.edu/artist/alexandrina-robertson-harris-2084
https://www.brooklynmuseum.org/opencollection/objects/92531
http://fineartdatabase.org/alexandrina-robertson-harris-1886-1978/