Why does Stephen sever her ties with Mademoiselle Duphot in the novel, The Well of Loneliness?

Mademoiselle Duphot was Stephen's French tutor until her father felt it was time to hire a more educated tutor. Years later, Stephen meets Mademoiselle Duphot on the streets of Paris, and they become reacquainted, often visiting with one another. Over time, Stephen becomes afraid that Mademoiselle Duphot will not understand her lifestyle and will push her away. Instead, Stephen stops visiting Mademoiselle Duphot herself.