In A Tree Grows in Brooklyn, how does Francie change because of the death of Johnny; the working world; and meeting and breaking up with Lee? ...

As far as the working world is concerned, Francie learns
about seniority, fairness, and the importance of reputation.  Francie becomes
disillusioned with the world of work after she has to cross the Brooklyn Bridge to get
to work.  She previously thought that the trip would be exciting, but quickly learns
that the commute is draining.  Once at work, Francie is happy that she is getting paid
so much because she has never before earned such a high salary.  However, after talking
to the other girls, she realizes that she is the lowest paid reader and that she has not
been treated fairly.  She becomes especially bitter when she realizes that she is a much
faster worker than many of the highest paid workers.  Francie, even though she feels
used, has no voice in the company and must continue reading for her low salary.  She
often looks at the top reader, who has a relationship with the boss, and wishes that she
could have her position.  So the working world introduces Francie to the hardships of
the "dog-eat-dog" work mentality.