Here are some thoughts/ideas....I teach GT students in 1st-4th grade, so I understand the difficulty in challenging a young child.
*Is there a 2nd grade reading group she could attend during the school day? Single Subject Acceleration
*Make sure she always has books that are at her reading level. This can be tricky because books at her level may not be appropriate for her age level. Check out hoagiesgifted.org
*Math Rules! is a great resource that she could work on independently.
www.piecesoflearning.com $19.95 includes 1st/2nd math
*If she has access to the internet, I have my students explore wonderopolis.org . She could do some research and create a poster, etc. to share with the class what she's learned about a certain topic. This is part of the Genius Hour movement.
*I focus a lot on vocabulary and comprehension with my first graders. Jacob's Ladder Reading Comprehension prufrock.com
Best of luck!