One of the goals for the "fashionistas" is to have unique items.. If you shop at a well-known, commercial brands such as H&M, Zara, etc. there's a high chance of getting the same clothes as your friend.
I think this can be a solution....
It is a Swedish shop where you can get unique items of hundreds of Swedish designers. You wouldn't know most of the designers of Tjallamalla. But they are very edgy and up-to-date.
Rings by Blimey
Clothes by Motel
Their off-line shop is located in Stockholm.
Photos are from their website: www.tjallamalla.com