What happened is that after Jennifer had wet her she then had shit in her panties. Just then her mother came in from going to the store. We see that she noticed that Jenny is crying. When she ask her what's wrong? Jenny just cried harder. It was then that she smelt a foul odor. Which she realized was coming from Jenny. We see that Jenny had after Kyle had said transform or dare had hit the rec. button on the phone answering machine. She goes over and sees why the lights flashing.
She listened to the message and realized that Jenny was acting like the way the message had said to. She also remembered that when her mom had been there recuperating that her mother had to wear adult diapers. She went into the bathroom and check to see if there was any of them left.