The “ideal” woman and her style changed very frequently throughout the 20th century. The following are drawings that try to capture such changes of each decade.
Tiny waist, full hips, curvy figure
“More modern, new woman”
Bobbed hair, shorter hem
rebellious clothes, bobbed hair, shorter hem, fringe
1930s-End of WWII
square shoulders, more masculine style inspired by war-time feelings
In a nutshell: