You reward her

You tell Emma she's a big girl, give her a hug, and take her to the bedroom... then you take out her magic wand and start running it over her wet diaper.

Soon Emma starts panting and gets close to orgasm. You take the opportunity to kiss her all over, holding her tightly as you press the wand against her wet padding. Your tongue explores every nook and cranny of her mouth, and she responds passionately. Then, with a sudden jolt, she reaches orgasm and lets out a cry of pleasure. She seems truly satisfied and relaxed.

While she’s recovering from her emotions, you put the blanket over her so she feels comfortable, and she goes to prepare a meal… as well as a smoothie.
When the meal is ready, you go to get her from the bedroom, and she wants to change her clothes. But you tell her that the meal is ready and that there’s no time to waste. You can change her later, at your leisure. With all the smoothies she’s had since the beginning, she’s becoming more and more submissive to your wishes and just goes along with it. So she ends up in a wet diaper for the entire evening.

Finally, you change her into a clean diaper and go to sleep.
The next day, after having breakfast and a smoothie for her, you decide to go for a walk in the park and convince her to wear another diaper. Of course, she’s hesitant at first. But you have more and more control over her, which allows you to make her wear one under her clothes. She still chooses an outfit that hides it somewhat, but you’ll take advantage of the walk and the smoothie she just drank to send her more subliminal messages.