It's a "phase" she will grow out of it.
Most people know jack $hit at that age. They experiment with different looks and personas most get over it eventually.
So the fact that you react to it probably means your becoming a grumpy old man rather than "judgemental bastard" which has no age restrictions.
" These young whipper-snappers thumbing their nose at society, put on some decent clothes young lady" ( said in Mr Magoo voice) lol.