How does rosaleen change once she is staying with the boatwrights? why do you think she behaves differently?

Rosaleen seems to change because the environment also changed. now she is with black females. Here, she had not the threat of white men who used to beat her up when she tried to exercise her civil right. lily noticed her sudden change as soon as she entered the house, while crossing the yard even though she was walking under the rain. 

Because anne thinks margot is jealous towards her and peters relationship.