Without going into product details and brands, the best razor for teenaged girls is the one that comes with at least two or more blades and has a movable head. You may experience some roughness when you use a razor for the first time, and that's the precise reason it's best to start slow. Also, make sure that you use after-shave lotions and ointments to prevent rashes. Some gels and products are meant to be used before using a safety razor.