While Ashlynn wasn't entirely comfortable with Isabell's rejection of fire, there was little to be gained from pressing her concerns now. Isabell still had much to learn in order to safely harness the extraordinary strength she'd gained in the power of wood, and she had enough ability in the remaining elements to use them as a sort of wading pool where she couldn't make significant waves while she learned about the duality of each of the elements.
Hopefully, by the time Isabell was ready to step forward as a powerful witch, standing on her own two feet, she would be more open to the nuances of her gifts.
