There are all sorts of theories about this one, but usually it breaks down to pretty common sense factors. These are, you both live in the same area so the stores around you are likely to be shared, you are friends therefore you have certain traits you like about each other, and similar taste is not uncommon (ask any female/female friends) and lastly you are most lkely a similar age which again narrows down the scope of clothing chioce. Of course it just could be plain out coincidence!