Gift Ideas for Twelve Year Old Girl

I was in a Coach outlet and bout my niece a bag for Christmas. It was on super sale and I know she will love it.

If you don't want to give a gift card, go to Claire's and buy a bunch of stuff and give a gift receipts. Most girls love that stuff.

Itunes
coloring books (yes!) from Dover Books
Amazon gift card (kindle books, gift card)

Is this for a friend of your kid's, or a family relative that you need to order and have it delivered... ? A cookie bouquet?
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ETA:
You really have to know SOMETHING about the child to make a good choice. My daughter is 12, and has very little interest in nails/hair/makeup/friendship bracelets, etc. All the "typical" stuff... she doesn't care about. She loves things like duct tape though. So a box with 5 rolls of various patterns/colors of duck tape would be loved! Or a gift card to a book store (of any kind, BAM, B&N, Amazon) would be an excellent choice since that is what she always is pestering us to buy for her: books. For a kid who doesn't like reading, maybe not such a good choice. This is also the age where they can go to a friend's birthday party and show up with a gift card for movie tickets OR a huge bag of gummy bears (found one at a bookstore once that was the size of a cereal box) or some other "favorite" candy/snack... and have both be equal "hits" with the recipient.
A lot of girls today are not "typical" and have their own sense of what is fun... not some prescribed age appropriate idea. If you know anything about this girl at all, it would help to share it here for the best ideas.

oh and here's a link to the "coloring books" I mentioned above. My daughter loves doing this stuff with colored pencils. http://store.doverpublications.com/0486444619.html

oh.. and yeah.. my 12 year old had about a year when she liked some things from Justice... when she was about 9. And she has never liked dolls of any kind, including American Girl.
Without any information on the girl, you need to go very general (like cash or a Visa Gift card).

Make your own jewelry kit?
Make your own candle kit?
Make your own friendship bracelet kit?

My first choice would be a gift card to the local book store, Barnes & Noble? I loved to read at that age & it's always good to encourage reading & it's shopping, double bonus!!

What us she in to? Maybe find her fave person/TV show from pop culture & look for a throw blanket or pillow or posters? IDK?

For your daughter? Or someone else? For someone else, I think gift cards are the way to go.

Is it a girl that you know well? If you don't know her tastes and preferences, I'd go with a gift card. You can ask her mom/dad where she likes to shop for clothing. Otherwise, I'd say an Amazon gift card or Amex/Visa gift card because she can pick anything. If you feel that you must send an actual gift, costume jewelry, nail polish kits, bath/bodyworks sets would be popular for that age.

I have an 11.5 yr old daughter. She loves iTunes gift cards, or gift cards to Claires Justice, or Target.

For her friends birthday gifts, she normally gifts them any of the above or cutesy stuff for their rooms (desk lamps, small dry erase or bulletin boards, fun accent pillows for their beds) plus the current issue of Tiger Beat Magazine and a big box of their favorite candy.

Gift card (Target, iTunes, Amazon, American Girl, Justice, etc)
Clothes (but you must know the style)
My kids love things for their rooms (you have to know the decoratin style)
Shoes

Really - gifts cards, or you need to know the child's style.

Wow. It really, really depends on the girl. Can you find out what she enjoys? If you can't, I also suggest you go with the Amazon card - and do ask her to let you know after she's used it; you're giving her a present, but you need to know what it is. (By the way, the comment about the Dover coloring books is right on. They're great! But again, you would need to know the girl's interests to know what to pick.)

How about giving some sort of "experience"?? Maybe she and her best friend could have pedicures? horseback riding lessons? make pottery? take an art class?

When I was 12 I would have liked art supplies. What is she into?

12 year olds are pretty diverse in their interests, just like adults. An itunes card for my near 12 year old would be useless, as she doesn't have anything to use it for. Justice clothes are kind of young for most 12 year old girls (and too small for many). My daughter would prefer science kits or books, so I don't think most of the suggestions offered here would work for her. If you don't know the girl well, ask.

Most kids that age love Itune gift cards...can be used on their computer, or ipod touch or if they have an iphone.