"Les Sisters" is a slice-of-life about two girls in present day France. Occasionally, they're superheroes -- in their imaginations.
But there was a spin-off series (2 volumes so far) where their powers are real. "The Super Sisters". The title of this one is "Private Laser".
The older one is given an atomic laser. The kid sister is too immature to have one, so she steals it. (I think. I can't read French either.) As you'd expect, things go downhill from there.