I read this book once when I was in middle school. A girl solves a murder or a mystery on a spaceship. It was a thin paperback books.
All I can remember is that there was an alien, and there was a movie star or actress or famous makeup artist on the ship traveling with another woman. By the end of the book the murderer was the woman the actress was traveling with who forced her to use her makeup skills to disguise her, and she was really some kind of alien.