Why is my Giant Day Gecko Trying to eat Charcoal?

I have a giant day gecko that has been acting strange recently. I notice that she (I think it's a girl, still pretty young but no signs of being male) was stalking something, even thou I didn't put any crickets in. Well she grabbed a small(ish) piece of charcoal from the substrate and attempted to eat it. I have never read about day gecko's eating charcoal so I tried to carefully grab it from her, but she ate it more before promptly shooting it out of her mouth.

Fast forward to tonight where she climbed down towards the substrate and bit a big chunk of charcoal. Just chomped at it a few times before sprinting back up the glass. Is this kind of behavior normal? Am I not feeding her the proper diet or something? Any help is appreciated, i'm concerned for this little crazy thing.

Oh also if it helps, her coloring looks normal (bright green and red) and she has quite the chunky belly.