I'm thinking and trying to put myself in the shoes of a young girl coming from a culture where the women are hidden behind yards of fabric. The clothing eliminates the shape of the woman underneath and then coming to another country where you can see a persons figure....all types of figures. How jaw dropping that would be. Would it scare me? Would it excite me? Would I want to wear the tank top with spaghetti straps or the baggy shirt? How does this young girl fit in her new world?
I lived and worked in Saudi Arabia for five years, working at a women only language school and was married to a Muslim (i.e. living with the local population not isolated in one of those western compound things).
Saudi women, and Saudis in general, are very familiar with western fashions and many wear them all the time (others were more traditional Arab styles of clothing that don't cover the whole body). The abaya (long outer cover, like a long dress) and headscarf are loose, very light clothing that's worn over the top of other clothing. At home, Saudi women wear whatever they want. To go out, they'll put an abaya and headscarf over the top, which they'll remove when they come back home, or when they go into a women only space. There are many women only spaces... entire shopping malls, universities, bank branches, schools (like the language school I worked at), beaches and all sorts. Little boys are allowed in women only spaces, up to around age 10 (the exact age will vary by establishment). Women don't cover up in front of men they're related to and homes have high outer walls so women can wear whatever they want at home and in their garden/courtyard.
Many Saudi women are into all the same hair and make-up and fashion things that you describe in your more recent post, and many little girls are too, and little girls don't have to wear the headscarf and abaya outside the house so there are lots of little girls wearing all kinds of fashion and pretty dresses, western and original, same as in the west. And there's quite a lot of American TV for adults and kids (dubbed into Arabic), so they see a lot of American fashions that way.
Plus abayas and headscarves themselves come in a wide variety of styles and are cut and designed to be very elegant. They're a fashion item too. Some little girls choose to wear abayas to look like their mothers, but that's up to them and their mothers.
I realise that you weren't talking about Saudi Arabia specifically, but I can't think of any country that has a more conservative dress code than Saudi. Other Muslim countries are like Saudi in that women wear whatever they want at home and in women only spaces, and just cover up in front of men they're not related to (which includes in public, generally, where men might be). The difference is they're less strict and you're more likely to see women who don't follow the covering up rules at all and just wear whatever they want, wherever.
IMO the culture shock won't be from seeing women in western fashions, but from seeing men and women interacting in the same places where women are dressed like that. Though from my own experiences and talking to loads of Saudi women (I taught English which included all kinds of student led discussions on topics of the student's choice) the Saudi women who don't agree with the dress code thing will lose the abaya and headscarf as soon as they step off Saudi soil and not experience any culture shock whatsoever. Saudis go to Bahrain and other nearby, less conservative countries to do all the things they're not allowed to do in Saudi. I lived in Bahrain for two years after living in Saudi, and every weekend and Saudi public holiday, Bahrain was full of Saudis (you can tell by a man's shmagh (Arab headdress) what country he's from, and you can tell by car number plates) doing things that are illegal in Saudi but legal in Bahrain. It's kind of hilarious in a way but totally understandable as Saudi has some really ridiculous rules. A classic is when you drive over the border between Saudi and Bahrain... (there's a bridge joining them and an island where all the border control is)... a car drives through customs and passport control, driven by the husband. As soon as they're officially on Bahrain soil, husband and wife change places and the wife drives the rest of the way. You see lots of people swapping seats in cars just after border control. (AFAIK women are now legally allowed to drive in Saudi, since they changed the law in the last couple of years, but it was illegal when I lived there. And there was a large, thriving business of private chauffeurs and taxi companies to drive women around. The language school I worked for employed 2-3 drivers just to drive the teachers and other staff to work and back.) Similarly, at the airport after a plane from Saudi lands, some women will lose the abaya and headscarf and be walking around Doha or Bahrain etc airport in skinny jeans and a cute top.
Note: some Saudi women will continue to wear their headscarf and abaya when not in Saudi out of personal religious conviction or personal preference. The bit above about not wearing the headscarf/abaya after leaving Saudi Arabia refers to those who don't agree with the dress code. My opinion is that women can wear what they want and cover up (or not) as much as they want and other people shouldn't tell women what they can/can't wear.