Ali S has a point. I wouldn't stress out over it.
If you are super worried then get her some gift certificates to her favorite stores. Then she can do the shopping for herself just like an adult.
My niece (11 also) loves getting gift cards. She actually prefers them to getting items. She likes to use them at the mall when she goes to hang out with friends, or spends hours shopping for just the right thing online at Amazon.com, Toys R Us, ect.. She never requests anything for Christmas unless it is something she really wants.
Also, one of the few things she has begged for this year is an American Girl Doll and American Girl books. These dolls are marketed to older girls that are getting out of the Barbie stage. They are expensive but collectable and of excellent quality. You can see them and shop for them at Americangirl.com .
I don't think any retailers actually carry them. You have to buy them online. Unless you want to pay next day shipping you may just get her an American Girl gift certificate.
One last idea. Get her a Lowes, Home Depot, and/or Target gift card and promise to help her redecorate her room. Girls this age love the freedom of creating their own space. You can limit her re-decoration to the amount of money on the gift card and no major renovations (like knocking down walls, moving outlets or windows, making built in furniture, and no attaching or gluing anything permanently to the walls, ceiling, or windows).
RPocai