Bambi Kramer (a pseudonym) is one of Jeans correspondence students. Her favorite artists are Walt Disney and Rembrandt. At least according to Jean, she's a terrible artist. She is mentioned in the final sentence of the story, which is kind of like having the last word.
Even though we never meet her, she is significant to the story. By observing Jean's treatment of her we can observe his changes in the story. Jean was mean and judgmental concerning Bambi and her art at the beginning of the story. While Sister Irma's work inspires Jean, Bambi's work depresses him.
By the end of the story, however, there is a reversal of this dynamic. Jean hasn't forgotten Sister Irma, but he never tried to contact her again. On the other hand, he apparently still keeps in touch with Bambi. This fact also suggests that Bambi is a good sport and has a sense of humor. Jean was horrible to her. She must have seen through to the fact that she was dealing with a teenager and taken the whole thing as the joke that it was.