How could the character Sue from "The Last Leaf" be described?

Sue is the pivotal and viewpoint character in O. Henry's story "The Last Leaf." She interacts with the other three characters, Johnsy, the doctor, and Old Behrman. She is also working for a magazine editor who may or may not accept her sketches and pay her the money she badly needs to survive. Sue is a struggling artist like Johnsy, but Sue is apparently more aggressive and more competent than her friend. Sue is a go-getter. She is spunky, aggressive--the kind of person who is likely to survive in New York and ever prosper. She loves her friend Johnsy, but she also depends on her for companionship and moral support. She wants Johnsy to survive because she loves her and also because Johnsy is the only friend Sue has in this big, cold, competitive city. Sue handles both the doctor and Old Berhman while nursing Johnsy herself and doing sketches for a magazine story.
It should be noted that when Old Behrman sacrifices his life to paint the last leaf on the wall of the adjacent building, he is not only doing it for Johnsy but for Sue. He is doing it to try to save Johnsy, but he is also doing it because he cares as much about Sue, who cares so much about Johnsy. If Johnsy were to die, that would not be the end of Sue's story. Sue would have to live on, and her life would be different--lonelier and much harder without her friend.
Sue is actually pretty bold to have come all the way from Maine to New York City by herself in those days. Her strong, independent nature is evident throughout the story; whereas Johnsy's passive, dependent nature is also evident. Johnsy needs help from Sue, the doctor, and Old Behrman. Sue has nobody to help her, but she is capable of looking out for herself and even looking out for Johnsy. Sue is courageous. She maintains a cheerful, optimistic attitude in spite of the fact that she is afraid for her friend and afraid for her own future.