Ladies what do you think when you see this?

when you see a nice looking girl who isnt wearing a bra? my daughter thinks it is a new fashion trend and she walks around without one. she says there is no law requiring one and she is fine. she is 16 and had dds. i try to force her to wear one but she just takes it off as soon as she is out of sight!!! the guys are going crazy over her!!! im kinda of giving up. what do you think?? i might have to just let her be.