P.S. I am not a witch or anything, but I do believe in the power of magic. Thank you.
You could try a freezer spell.
Citrine (stops bad behavior)
On the paper, write your niece's name and what you would like for her to stop doing. Fold the paper into thirds. Fill the freezer bag one third full with water. Put the paper and the citrine in the bag, zip it, stick it in the freezer, and leave it there.