Damage was definitely something I was assuming as part of the package- since exhaustion/low energy runs with the typical consequence of her fire magic I'd say that exhaustion is perfect as an added drawback to the spell! (Damage Retention doesn't seem enough on its own haha...)

Considering how exhaustion hits with just the fire stuff, I'd even say that if she pushes too far with this spell she should end up passing out. This is way bigger than casting a bunch of fire balls after all.