What is the main conflict in Belles on Their Toes by Frank B. Gilbreth?

"Belles on Their Toes" by Frank B. Gilbreth and Ernestine Gilbreth Carey tells the story of Lillian and her children. After her husband's death, the woman was left to earn the income for the family and raise 11 children on her own. This isn't easy to do at any time and much less in the pre-World II era when women didn't generally work outside the home, and certainly not in the field of engineering.