What is the most likely reason that Millie decides to put snow in Kacey's backpack, purse, and locker?

She feels like the bullying has gone on for long enough.
She thinks the Miserables are getting meaner over time.
She wants to show off to her classmates what she can do.
She is tired of Mother Nature not letting her use her power.

The most likely reason is: She feels like the bullying has gone on for long enough.