User blog comment:Ragadorus/Mystery Shell?/@comment-4123264-20130617024736

I like the pre-charging idea for her Neo moment, considering we didn't see any hits of that magnitude later on, but I've got a few possibilities to lay out on the table, too.

It might be a reference to Red vs. Blue: Season 10, when North emptied a spent bullet shell from his sniper rifle despite not firing it before on-screen.

Another theory of mine is that the standard form needed the bullet to boost her strength, and it's only when they're active that her punches start bursting into flame.

Or we could be looking into this too deeply and it just happened because it looked freaking cool, and we gotta DEAL WITH IT. 8J

Regardless, the chances are high we'll never get an explanation for it.