Russell and Deary, both 30, became engaged last year. Russell is expecting her first child this summer, Jill Fritzo, the actress' publicist, said last month.
Russell portrayed spirited college student Felicity Porter in "Felicity" for four years. The series ended in 2002.
She starred in the films "Mission: Impossible III" and "The Upside of Anger," and the TV miniseries "Into the West."
Her new movie, the independent romantic comedy "Waitress," was screened at the Sundance Film Festival last month.