How is Holly planning to escape?

Holly is banging the bed against the wall and floor. She does it while she keeps her head in her hands as though she is crying while banging the bed. She uses this as a distraction as her goal is to break through the floor enough to find dirt. Once she can uncover some earth, she can plant the acorn that she has in her boot. Once the acorn is planted in the dirt, Holly will regain her magic. Then she can easily escape from the cell that they have her in.