Who is Maria Petrovna Dunaev from We the Living and what is their importance?

Maria Petrovna Dunaev is Galina's sister. Once affluent, she has been reduced to the level of a pauper. She has aged dramatically, no longer the beautiful woman who was once the subject of paintings and poetry.

Over the course of the novel, we learn that Maria is sick and coughing up blood..... something she tries to hide from her family. Kira is called to Maria's home when she is about to die, and she tries to comfort her in her final moments of life. Before she dies, Maria cries out to Kira that she wants to live. When Kira arrives home from that horrific scene, she finds Leo coughing.