Somethings you want to consider
1. what do you want it made out of?
Yellow Gold, White Gold, Silver, or purely costume jewelry
(this will be dependent on what you want to spend - I'd probably vote for silver)
2. What length do you want the necklace
This might be dependent on her wardrobe
There are chokers (which wraps around the neck, often is usually made out of a stretchy ribbon type material), a 16-17" lenth which sits right at the throat - if she wears a lot of open neck tops, this is a great length, there longer lengths, sometimes whcih can be wrapped around.
3. What do you want it made out of?
Metal, Gemstone, Pearls (freshwater or cultured, or fake pearl in color) or a combination
4. What's her style?
A strand of pearls (which can be expensive, but are beautiful, but if she's the funky type, she wont appreciate them. Does shelike pendants (which is a stone or something hanging off of a chain, or something a little fuller.)
When I have time, I make jewelry, made a beautiful amethyst and silver for a friend for Christmas - I ended up making it because I couldn't find something unique looking. and amethyst was chosen because of some of the meanings of the stone.
http://kiwijewels.com/gemstone_meanings.htm
Does she have a favorite color? Maybe a gemstone in that color...
I just did a quick google on silver necklaces - and came up with this store (among a few thousand others) This one has some interesting stuff - that might give you some ideas (The Tiffany inspired stuff - -is copies at a real price that Tiffany's sells)
http://www.evesaddiction.com/tiffany...necklaces.html
THis is their entire collection:
http://www.evesaddiction.com/necklac...laces.html#top
Browse thru them -- they have all different styles -- see what catches your eye - what you like and what you think she will like - -then that can help you narrow down your search.
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Now just remember- -you are putting thought into this-- so she is going to love it and love you (if that's OK) for taking the time to try and find something she will like. You get major points for that.