Have you checked out our Gifts http://beta.savvyauntie.com/GiftSearch1.aspx section? You can filter by niece/nephew, age, price... and most importantly, her personality.
American Girl and Barbie are good ideas (although Mom may have opinions about Barbie... one Auntie I know made THAT mistake!) But she may also be into Hannah Montana, High School Musical or the Jonas Brothers.
If she's crafty, you may want to consider a craft kit or art set. If she's a sporty adventurer, you may want to consider a new bike - but don't forget the helmet! And if she's an avid reader, you may want to get her started on a book series....
Next time you speak to her on the phone, ask her what her friends are into.... it may be easier for her to tell you about what she wants by referring to them.
Anyone else have specific gift ideas for sehparks?