Maddie was having a tea party with Sparkle in her room when her parents called her to join them for dinner. While Maddie wanted to continue having a tea party forever, Sparkle instructed Maddie to go and allow Sparkle to clean up for her.
Maddie agreed and left. When she finally returned, she found Sparkle dead and her room covered in blood. She screamed in horror and dialed 911.
This alerted Sam and Dean Winchester to the scene. Since her parents couldn't see zanna, they didn't believe the problem was real and her mother ended up getting covered in blood without knowing. This lead Sam and Dean to instruct the family to have a hot, purifying bath to clean them.