This is book number 5 in the Dragon Girls series.
Aisha and her friends Mei and Quinn have an amazing secret: They can transform into powerful dragons. Together, they are the Treasure Dragon Girls, and they help keep a realm called the Magic Forest safe from harm.
The evil Shadow Sprites have stolen the Magic Mirror, determined to cause chaos among the forest’s animals. Aisha must harness the power of sapphires to rescue the mirror, and return it to its rightful home in the Magic Forest's secret vault.