Tina's casual mention of Leah's age not being that of a toddler was enough to cancel out the trigger to make her think she was three.
Leah ripped her thumb out of her mouth, suddenly aware that she wasn't a toddler. She was a teenager. She was a teenager sitting in the seat of a shopping cart, wearing toddler clothes, pooping in a diaper!
As Leah continued to grunt, pushing more poop into her diaper, she realized that her diapered state wasn't the problem she thought it was. Thanks to Tina saying Leah knew she needed to improve her potty training, Leah was actually glad she was now diapered. She wouldn't wet the bed or leave skid marks in her underwear, and could focus on potty training with Tina.
But Leah was very unhappy that she was dressed like a toddler and had been forced to act and think like one. Another cramp rippled through her abdomen, making her adjust her seat slightly for a better angle and push harder. She steamed at her current state. Yeah, she needed diapers, she knew that and had accepted it. But did they have to be for toddlers? There were diapers for teenagers with incontinence!
"Gosh, your poopy face is so cute," Tina cooed. She ruffled Leah's hair. "I wish you would suck your thumb again, though." Obediently, Leah's thumb found its way back to her mouth. With a final grunt and push, Leah finished pooping. She sat back with a sigh of relief. "Phew, you're stinky! I better get you changed."
Unable to help herself, Leah continued to suck her thumb as Tina pushed the cart towards the bathrooms. Her mind was racing. She had to avoid someone (namely, Tina) making her think she was a toddler again. But she didn't know how to do so. Tina liked when she acted like a good toddler, so she wouldn't likely make negative command comments. But if she leaned into acting like a toddler, Tina might encourage her behavior.