well i can tell you that i am living in south korea right now and that there are few spots where you can find international english magazines.
that being said, it's certainly possible. they are at most LARGE bookstores (ie Bandi & Looni's) and maybe a few shops in Itaewon (in Seoul).
still, tell your friend to bring a bunch of cash, because it will cost her about 20,000won (approx. US$20.00) for a single copy of US, British or Paris Vogue -- more for Vogues from other countries.
other magazines (ie Numero, i-D, V, etc) are waaaaaaaaaay more expensive. I wanted to by the newest V Man mag the other day, but it was about US$50.00. so i had to pass.
if none of that matters to you, then tell her her only hope is right in Seoul, and then in a foreigner heavy area like Gangnam or Itaewon.
hope i've helped!