Who is Ms. MacTrough from Rainbow Boys and what is their importance?

Ms. MacTrough is the art teacher at the high school Jason, Kyle, and Nelson attend. It is unclear whether she is gay, but all the students suspect she is. She has been nicknamed "Miss Mack Truck" or "Big Mac," which is the only clues to her physical description. Ms. MacTrough is the only teacher at the school in support of the Gay-Straight Alliance Kyle and Nelson hope to start, and she fights for the school to recognize this newly formed student organization.