Startle her so she drops the glass

Being the dickish spirit that you are, given you have taken over the body of another and are going to use it to fuck said person's own flesh and blood relative, the chance to startle someone was just too tempting to pass up. So you shout out loud behind your mother, and she litterally jumps up in fright as she drops the glass that had been in her hand. It hits the floor and shatters into multiple pieces.

"Brandon!" she says as she holds her chest to slow down her breathing a bit, "You startled me. What are you doing here? You're supposed to be on your way to school."