I was doing a bit of research on what house Moaning Myrtle was in.
As far as I know, it is never mentioned in the books, so I tried to figure it out from her movie uniform. Anyhow, this is what I ended up posting:
As far as I know her house was never stated in the book.
Since I couldn't remember what uniform she wore in the movie, I went back and re-watched parts of my "Chamber of Secrets" DVD, but I couldn't make it out. All I could see was what looked like a Hogwarts crest.
Anyway, I did a bit of research and apparently at least one site said this:
"The Hogwarts uniforms changed from fifty years ago to the present time. The fifty years ago uniform had the Hogwarts crest and a pin to tell which house the students were in. Notice how Moaning Myrtle's pigtails always cover her pin, for what house she was in was never mentioned in the books or movies. This is especially clear when Harry, Ron, and Lockhart go into the bathroom to find the Chamber of Secrets."
The site was a HP trivia site. You can find it at:
http://www.moviemistakes.com/film2434/trivia
I also found this interview with Tom Felton (Draco Malfoy) and Shirley Henderson (Moaning Myrtle).
"Lizo: There's been a lot of speculation on the internet earlier about your uniform and what house Myrtle was in when she was at Hogwarts - I've been trying to look at it but I couldn't quite see.
Shirley Henderson: I can't remember what it is.
Tom Felton: I'm sure it was Ravenclaw."
One more little tidbit that I uncovered was this:
"And we think we solved one mystery that no one's ever had the answer to before. She wore a blue uniform - which means she must have been in Ravenclaw house."
I found that at:
http://news.bbc.co.uk/cbbcnews/hi/tv_film/newsid_2526000/2526767.stm
The problem is I don't know if the above quote was based on observation of the film or on the actual uniform she wore. If they were watching the film, then they saw the ghostly Myrtle which makes it hard to tell color.
To be safe, your friend could do a Hogwarts patch and tie instead of house specific ones and cover where the pin should be with her ponytails (if possible) like they did in the movie.
I'm sorry I didn't see your message earlier. My post may be too late for your friend to do much about her Halloween costume.
I hope this helped.
YolandaThe above post reminded me of a thought, I've had before, but never posted which is the difference between the book and the movie uniforms.
In the book, Harry and Ron don't know where the Slytherin common room is and they stop a girl to ask her. She responds "I'm in ravenclaw", so obviously the book uniforms do not denote house. This same mix-up couldn't occur in the movie, because the movie uniforms are house specific.
The movies aren't the only images we have of Hogwarts students in house colors either. Some of the illustrations for the HP books have Harry, for one, wearing a red and gold scarf.
Least I forget, the Harry Potter Sorcerer's Stone/Philosopher's Stone PC game has color coded robes so they are house specific too.
Anyhow, in the book, they wear "black robes" and they also wear hats to class not just on special occasions like in the movie.
Anyhow, I'll have to add more about the book uniforms later. I finally sat down and put one of my random thoughts into a post, unfortunately for all of you reading this it wasn't one of my more relevant ones. Oh, well.