We talk a lot about proper arrow spine and tuning and what not on this site. However in your case I wouldn't give it too much thought yet. She probably is not good enough to notice the difference in an expensive perfectly spined arrow at this point. Nor would I spend a ton of time on tuning. I would get the bow to where the arrow leaves reasonably straight and leave it alone. She is not going to hunt with it right? You can get away with a lot target shooting at 20-30 yards with target tips and good fletchings.

I would try not to get anything too heavy though. Just get some youth carbon arrows or some easton jazz arrows with glue in points and let her shoot. A local shop should be able to help pick a usable arrow for her set up.

Right now I would concentrate on if the bow fits her well and proper form. These are the MOST important factors in being able to shoot well. After she gets good I would look into getting good well matched arrows and doing some fine tuning. My first goal would be getting the draw length right and getting a good shot sequence down pat.

Good luck,
Paul