Leah feels very confident that this particular incident happened because she was sleeping. When she's awake, surely she won't use her diaper! Or, at the very least, she won't mess herself. And because she won't be sleeping anywhere but Rita's house, she doesn't need to worry about protection when she leaves.
When Tina and Leah go inside, Tina gives Rita a crash course on how to change a diaper. Leah is upset; she can change herself! But she doesn't protest too much. Rita says that she'll ask before changing Leah anyways.
Not that Rita will ever see Leah in a dirty diaper. If Leah has more nighttime accidents, she can just change herself first thing in the morning.
At first, things go the way Leah plans. Despite her best attempts to use the bathroom before bed, she wakes up the first and second morning at Rita's in a full diaper. But she's able to hurry to the bathroom and change before Rita notices. Leah knows that Rita expects her to use her diaper, but she doesn't want to do so in front of her. After all, Rita will be reporting back to Tina.
Unfortunately for Leah, her plans go awry on her third day, when...