Why is Marija trapped in the life of a prostitute?

Marija tells Jurgis of the whore trade, how girls are brought over from foreign countries and forced into prostitution. Their madam gives him morphine so that they become addicted and reliant on staying in the brothel to afford more of the drug. She tells him of how women, contrary to opinion, do not like such work, and how they are forced into such labor by starvation and poverty.