What is the name of the 30s or 40s movie and who was the actress?

One night I was watching an old movie, I think it may have been either
Cary Grant or Gregory Peck. I did not watch the whole thing and then
another night I happened to tune in when it was playing again at just
about the same place as before but still did not get the name or
anything.

All I remember is that the female lead played a really ditzy dumb
uptown girl who lives with this guy who is really mean to her. He
makes fun of her and bosses her around. The male lead (whoever it was)
is a really nice and educated man, there's a scene when they are
outside and she is reading something with glasses on. He is trying to
educate her because she is tired of being dumb. I think she even
leaves her husband and the male lead helps her.
I would like to know the name of the movie but more so who the actress
was because I think Madonna used her as her inspiration during the
making of "Who's That Girl". In that movie she has a very Betty Boop
and Marilyn Monroe-esque persona. As a matter of fact, the first time
I saw that movie i was about 5 and it was my favourite movie. With the
cartoon during the intro credits I always thought it was supposed to
be Betty Boop and later realized it was Madonna's character.
Anyway, she has gone through so many phases in her career, Hollywood
glamour girl/pinup was just one of them for a time and would really
like to research the actress who was in this old movie.
Any ideas?