Hello there, and thank you for your comment!
Currently, I'm working on making the entry levels a little less difficult, so I'll make sure Aqua is less terrifying as well.
As a suggestion, try leveling up Gura until she learns the skill "Hydrodynamic Shark", which will grant her 100% Physical evasion for 3 turns, basically making her invulnerable to all of Aqua's attacks, so you just have to pay attention to keep this buff on her