What person wear purple mask, and she is 10 years old girl

It sounds like you might be describing a character from a show, book, or movie. One popular character that fits that description is **Amethyst** from the animated series **"Steven Universe."** She is a gem with a purple color scheme and has been depicted as a young girl. If that’s not who you’re thinking of, could you provide more context or details about the character you have in mind?