Frado is like Cinderella, raised as an outsider in the same house as a hateful, judgmental "sister," Mary. Although not technically sisters, Mary's vengeful approach clearly shows that Mary is offended that other kids at school might think she and Frado are cohorts. In other words, Mary has a prejudice against Frado for being half black. She believes that she is better than black people, and suddenly, she is stuck with Frado at school and home.
The involuntary pair show a problem. Mary is upholding prejudices which are being challenged by her natural emotional responses to Frado's suffering. Mary doesn't like that she has to feel sorry for Frado's abandonment, so instead of allowing those emotions to manifest (which would lead to her viewing Frado as a real human being), she goes the other way. She hates Frado (a literal orphan) for being in need.
This portrait of slavery and of racism is troubling for many reasons, but this is especially worth mentioning: Frado is the victim of true abandonment by a flippant, fickle mother who clearly shares the feelings of loneliness, rejection, and frustration. That is a portrait of Frado's journey to be at peace even when she is surrounded by hateful people. She will have to offer herself what her own mother failed to give—hope and love.
