Only explanation I have for Mia hitting as hard as Cheryl's magic is so the party's balanced out and both members have their own niche. Though story-wise I'll just say that Cheryl's age caused her powers to not be as effective as they were before, and/or that Mia's actually quite athletic thanks to swim club, though they may sound like hand waves more than anything.
I did initially have plans for more optional areas but they were a bit too ambitious to include in a jam game, not exactly sure if I (or my brother) would be up to create a larger scaled post-jam version. But there is an optional boss rush where it takes place back in Mia's house, and it unlocks right before the final area.
As for the next time you attempt the Camazotz battle, have Mia tank with Textbook Guard on first turn, it's a lifesaver.
Overall, I appreciate the feedback!