A pretty ring for everyday wear -- maybe not a precious stone, per se, such as a ruby, but something that goes with one of her favourite dresses/outfits.

Or a gorgeous set of dangly earrings (does she have pierced ears?)

Go to one of her fave boutiques - the kind that have a lot of jewellery on display as well as clothes and stuff - and you might spot something.

A chic handbag. The best (read: trendiest) ones are designer - Prada, Gucci, Chanel - and most good handbags are quite spendy, but if you want you can source some good quality leather knockoffs (but don't try to pass it off as the real deal, natch) OR try a department store for (somewhat) less outrageously expensive brands. Or Ross, Marshalls...

I can only think of girly things. What are her hobbies? Get her a snowboard? A saddle for her horse? A new set of tires for her racing car??

Perfume is always welcome! I love Chanel's Gardenia -- it's a very pretty scent that never fails to gain compliments and can only be purchased at Chanel stores. I wear that or Chanel #5 on a daily basis, but that's just me...

Most women wear the eau de toilette or the eau de parfum -- the real deal is comes in a tiny bottle and is used sparingly, but when used under the lighter (more diluted) versions, once that top layer wears off, the true, pure perfume lingers beneath.

So, find out if/what perfume she wears and buy her a small bottle of the expensive version.

Hope this helps.