Such a thief...maybe because the ability itself was acquired by stealing other people's energy or whatsoever so it had this weird characteristic.
Anyway, Ainsley was afraid that if she weren't careful, the ability would suck her energy core dry, and then she would die in an instant!
But Ainsley soon found some tricks to save up more energy when drawing, and that was to avoid mistakes so that she didn't have to redo the drawing.
Even if the outcome weren't as perfect as when she redo the drawing, it would save up more energy and wouldn't waste energy.
Drawing directly in the air also saved up a lot of energies used to create the drawing tools!
Even more awesome was the fact that Ainsley could change the surrounding air to have her tab's feature.
She just had to imagine it because everything and anything could be a medium to draw.