"No, she doesn't know you're really a teenager," Tina says to her diapered stepdaughter. "She only babysits for free if the relative is under a certain age, so I told her you're two."
"Two-year-olds don't always need diapers," Leah argues.
"Yes, but in order to sell your age, you need the extra youth the diaper gives you," Tina replies. "You don't have to use the diaper, just wear it. I told Rita that you're working on potty training, so she has a training potty for you to use."
Tina is lying. Her sister is childless but loves kids, and babysits for free regardless of age. But she's noticed Leah sneaking away to the bathroom after sneezing and running a lot of loads of laundry that don't have much in it. In particular, she's been washing her sheets a lot. It doesn't take a genius to figure out that Leah's having accidents and, like a teenager, pretending nothing is wrong.
Rita loves kids but hates bodily fluid messes in her house. Tina doesn't want Leah to pull this behavior of having accidents and then covering them up at Rita's place. It would really upset her, particularly because Leah hasn't been doing the greatest job cleaning up after herself. Tina has had to step in (without Leah knowing) to properly get her bed, clothing, and furniture free of urine and, on rare occasions, feces. With Leah's refusal to admit her problem, this is the only solution.
But she is telling the truth about Rita thinking Leah is two and potty training. She wants to save Leah some face and also still give her the chance to use the toilet. Who knows, maybe this will actually serve as a touch up on Leah's flagging potty training.
Tina gets Leah loaded up in the car and they head over to Rita's house. Tina looks at Leah in the rearview mirror. Leah seems deep in thought in her car seat, staring out the window in contemplation. Tina can't help but wonder how Leah is going to handle a week pretending to be a diapered toddler with Rita.