Lovely Frances Dee
She was simply luminous in this film. And her underplaying is a great contrast to Bette's high-powered histrionics.
Interesting note: according to her imdb.com biography, Frances and her husband Joel McCrea were, in the 1970s, rumored to be worth between 50 and 100 million dollars. Hoowee! They were married 57 years, and were surely one of the most beautiful real-life couples ever in Hollywood.