When making Gingerbread Girls, you'll want the icing to be fairly stiff for piping designs, trim, outlines or faces, or for gluing fondant shapes or dragees in place. For painting larger areas, thin the icing slightly with water so it's the consistency of paint.
In a large bowl, beat the egg whites at medium speed until foamy. Add the confectioners' sugar, 1 cup at a time, beating between additions until the sugar is completely incorporated. Add the lemon juice and beat at high speed until the icing holds its shape, about 5 minutes. Thin with water as needed.
If you have any concerns about eating uncooked eggs, you can make this icing using pasteurized egg whites or powdered egg whites or with an instant royal-icing mix.