(written from a Production point of view)
This page contains information regarding Star Trek: Short Treks, and thus may contain spoilers.
Rebecca Alie Romijn (born 6 November 1972; age 47) is an actress and former model. She played Una in the Star Trek: Discovery second season episodes "An Obol for Charon", "Such Sweet Sorrow", and "Such Sweet Sorrow, Part 2".  Romijn reprised her role in the Star Trek: Short Treks episodes "Q&A" and "Ask Not".
Romijn is perhaps best known for playing Marvel Comics character Mystique in the first three X-Men films directed by Bryan Singer and co-starring Patrick Stewart, Famke Janssen (like Romijn's father had been, a Dutch-born national), and Kelsey Grammer.