well informed yid – i agree 100% to the begining of your post that it stems from a desire to be like the goyim. However, i truly beg your pardon but – MANY MANY MANy frum homes DO NOT allow any goyish books, magazines, newspapers etc into their homes yet their daughters still have such a deep desire to be “with it ” Stylish, and many times NOT in a tzniusdike fashion. it’s simply because we live in golus, and whether we like it or not we are effected by the society around us.
Really this is the route of tznius which many have already posted. That I am different, i am a bas melech, i am royalty why should i care what the “peasants” (goyim) dress like. I’ve already said this once here i think but its worth repeating. Once of the speakers on bnos melachim said it so well, the story with Queen Elizabeth and her visitor was wearing the same thing as her and felt so embarrassed, she apologized profusely and the queens response was something like “the queen doesn’t look at/care what others wear” i don’t remember the exact wording but something to that effect. If we instilled in our daughters a DEEP DEEP sense of pride that we are royalty – its really the shoresh cuz no one can imagine a real royal person dressing in an undignified way.