I think it's great that she is interested!

If she wants to wear a kilt by all means get her a kilt. If she prefers a Fraser, then a Sportkilt would be the easiest and cheapest option off the rack. The Men's Small is just the next notch up from the youth size. They could do a custom job for you as well. Or might sell you their poly blend fabric if you are handy with a sewing machine. That could be another project you and your daughter share?

Next up in price and quality would be a USA kilt. I'm sure the folks there could build in some growing room. But not too much, you want her to enjoy the fit now.

Enjoy,
Moosedog