Walter matthau film about a rich lady?

You're likely thinking of the 1979 film "The Great Santini", starring Robert Duvall as Lieutenant Colonel Bull Meecham, a decorated Marine fighter pilot who struggles to connect with his family. While Walter Matthau doesn't play the wealthy lady, he does play "Sergeant Major", a gruff, demanding Drill Instructor at the Marine Corps Air Station.

The wealthy lady in the film is "Mary Anne Meecham", played by Blythe Danner, who is the wife of Bull Meecham. She is portrayed as a strong and independent woman who is trying to raise her children in a peaceful environment while coping with her husband's difficult personality.

It's important to note that there is no Walter Matthau film featuring a story centered around a rich lady as the main character.