Part of the problem in understanding this plot is that the daughter herself has been so shell-shocked by her embarrassment and shame about her mother, that she has a hard time differentiating what it is exactly that she doesn't like about her mom. It would be easy to say that she hates her mother for being a prostitute, but actually, when Josie suspects her mother is guilty of a murder, the implication is that it isn't just how her mother makes her money that bothers Josie, it's her sociopathic tendencies.
In the end, the novelist shows that Josie overcomes the temptation to become a prostitute like her mother, but it isn't clear from this that prostitution is evil or that Josie has mastered her fate. Of course to make money some other way is obviously preferable, especially given the trauma that prostitution has caused in Josie's life, but ultimately, her goal is to establish her own identity, and that process is not completed in the novel. However, in the climactic moment when Josie walks away from easy money, "Out of the Easy," so to speak, she does symbolically begin the journey of differentiating herself from her mother.
Another problem understanding the plot comes from the fact that (just like in real life) prostitution means different things to different people. For Josie, it represents the parts of life she disdains, like judgmental people, money-hungry people, abusive people, and most of all, the shame she feels being the daughter of a woman she does not respect. Whether it is judgmental for Josie to think less of her mother for sex work or not, it is clear that she has been seriously hurt by her mother's lack of integrity in many ways, not just the compromise that prostitution represents.
