Hmm...is this unusual for a woman to be wearing a tie and a derby hat, even back in the 30's? I find it rather stylish, but was wondering about the gender thing. Perhaps she was going to a Charlie Chaplin look alike thing!
It's her riding attire, it does look rather striking in some of the other pictures. I'll scan one of the photos which shows the jodhpurs. I think they wear those hats for some equestrian activities.
Duh! Now that mention it the answer is obvious about the riding outfit!