So I went and did some looking around online and was somewhat surprised at how many legitimate links turned up when I Googled "guided meditation, children". Some of it might need to be modified somewhat to work for your situation.
Guided Meditation for Primary Students. This one seems like it's specifically focused on using guided meditation in the classroom, but if some of her anxiety is coming from school, then these might be helpful for her if she starts feeling anxious while she's at school and you're not there.
Relaxation Scripts for Children
And another script CDs and Mp3s are also offered here for kid's meditation and relaxation.