The answer is that Eve’s powers are limited first and foremost by the mental block discussed in the special, and second by her own reaction time and imagination. Third, excessive use of her powers has been shown to seriously fatigue her. The little energy discs around her hands likely take far less energy than would be needed to transmute an entire legion’s worth of rifles into sand.
If you read the comics, she does come into her own a bit, and builds up her ceiling just like you’d expect for a superhero show. But we’re still early days for Eve. Can’t make her Dr. Manhattan overnight. She and Mark need to build over time. If Goku could access all 15 levels of super Saiyan (or however many there are now) by episode 10, why watch the rest of Dragonball?
TL;DR let her cook
There’s no comments because there don’t need to be. Fuckin Clancy Brown dude. Thread over.