Despite Tina's instructions, Rita does not remember to put the laxative in Leah's breakfast; Tina was trying to be discreet, and unfortunately did not put too much emphasis on the 'vitamins'. Rita was already unexperienced as a caretaker, so it slipped her mind. However, it turns out to not be necessary. Leah woke up the next day in distress upon finding her diaper is heavily used, and becomes even more distressed when a harrowing cramp leaves her filling it more; the laxative was strong enough that it's effects lasted throughout the night.
Not just that, but ever since Leah's toddler acting experience, her grasp on her potty training has become rather tenuous. She had never truly gotten past having accidents, having difficulty with her continence most of her life; dressing up and acting like a toddler for a day had done something wacky with her brain, making her have a far more lax relationship with the bathroom. She held it longer, felt it less often, and started wetting the bed every other day---the massive accident Leah had before may have been caused by the laxative, but it did irreparable damage to her potty training.
She walks into the kitchen with a sagging diaper, embarrassed and on the verge of tears. Rita smiles sympathetically and takes her to the changing table to change her diaper. By the time they return to eat breakfast, Rita had already forgotten about adding a pill. Regardless, Leah ends up pooping herself again while eating, caught completely off guard as her awareness of her need to go is completely shot. Leah wasn't too concerned about her rising diaper dependency, but it's clear by this point that it's not something that will simply go away.
Realizing that she truly is at risk of losing her potty training, Leah...