Mystery Party Games are traditionally quite difficult to organize. However, this need not be the case with this idea.
Either in advance of the party (to allow the girls to come in fancy-dress) or at the start of the party, give each girl the name of a character that they have to play during the party (e.g. variations of famous singers or actors).

photo credit: Photo Mojo
Each girl will also need their own secret which you can give them on the day or which they can make up.
Using their character, each girl must try to find out as many of the other girls’ secrets as possible.
