This poem has a literal side and mythical side to it meaning. The literal side would just be that it is about two sisters with different aspects. The mythical side could be referring to the two sides of Persephone to show the connections between "shade and light".
In the first stanza, it introduces the two sisters, different as dark and light. One sister is very happy while the other is awfully depressed.
In the second, third, and last stanza, it talks about the aspects of the sister of the shade side. This sister is a logical, mathematical, and thinker sort of person. She spends her time…