Käte Traumann Steinitz (August 2, 1889-April 7, 1975) was a German-American artist, photographer, collector, writer, librarian, and expert on Leonardo da Vinci.
Biography on Wikipedia: https://en.wikipedia.org/wiki/Kate_Steinitz

Young Girl by Käte Steinitz / 1939 / Watercolor and chalk / Sheet: 17-1/2″x12-1/2″
UCLA Grunwald Center for the Graphic Arts at the Hammer Museum, Los Angeles, CA

Käte Steinitz on Artnet: http://www.artnet.com/artists/k%C3%A4te-steinitz/

Further reading:
https://arthistorians.info/steinitzk
https://www.ma-g.org/artists/kate-steinitz/
https://collections.lacma.org/node/178972
https://www.fembio.org/english/biography.php/woman/biography/kate-steinitz/