Seriously? You're focusing on the wrong thing. Hydration helps, but no amount of water fixes a bad dive profile. The only thing that truly matters is following your computer or tables exactly, and making your safety stops. Food won't save you from rushing to the surface.

Yeah, skipping the prep work is so true... My cousin rushed painting his room without taping the edges first. Had streaks all over the trim and had to redo it, which totally echoes what @piperg10 said about things falling apart. Spent more time cleaning up the mess than if he'd just set up properly.

Small adjustments and steady breathing have ALWAYS worked for me in those moments.

What age is she? I messed up with my cousin's kid by going too dark too fast. For under 10, you can't go wrong with the "Bone" series by Jeff Smith. It's all cute cartoon characters having a big fantasy adventure, so it feels friendly. For something more modern, the "Amulet" graphic novels are a huge hit, my nephew blew through the whole series. Just avoid the classic superhero stuff at first, the continuity is a nightmare.