We previously published this post on February 28, 2023. Since then listeners have been writing with additional details. I've collected their updates below. Forgive me (and let me know) if I've left someone out.
On Sept 6, 2023 Rich Bowen writes: " The surname “Wold” was first given in The Peanuts Movie, but the name “Heather” was first used in the 1976 special “It’s Your First Kiss, Charlie Brown.” That was the first special after the death of Vince Guaraldi ended what’s considered the “golden age” of Peanuts specials, and where they started loosening some of the “rules” of the Peanuts universe. Heather appeared in several specials but never spoke, and her appearance was inconsistent. But while Heather had a name and a face in the cartoons, that was never considered “official,” and according to the official Peanuts Trivia And Reference Book from 1986, the Little Red-Haired Girl’s name is unknown."
Puey McCleary commented on 1971 Part 2 : Okay, I thought I was the only one using ChatGTP for "Peanuts" related nonsense. I asked the Chat a bunch of questions, and it kept telling me that The Little Red Haired Girl's name was "Marsha" (or something like that). I told the Chat that she's called "Heather" in the television specials. So, if, in the future, Chat calls her "Heather," it may be my fault. Be ye of good cheer.