Miss Helen's role as an artist in the story is to provide spiritual comfort for herself. Years before the story takes place, Miss Helen's husband died. It was then that she started to no longer attend a traditional church service. Her "church" became her home, and her worship became her artistic outpourings. Her art, with the manipulation of light and dark, helped her keep spiritual darkness away from her. It gave her comfort in this life, not necessarily any guarantee of an afterlife.
Between Miss Helen and Elsa, the two ladies function as a counterpoint to traditional religious beliefs. Pastor Marius represents the traditional Judeo-Christian religion, which is not painted in too positive of a light in the story. The play shows the Christians as people that abandoned Miss Helen. Miss Helen shows the reader the idea that a single religion isn't important. What's important is how a religion gives a person comfort. Elsa supports Miss Helen in this opinion by encouraging her to keep doing her art.