She likes to wear them

Lilith Clawthorne was waking up one morning. She looked down and smiled at her current attire, a loose-fitting T-shirt, and a thick diaper that she had used in her sleep.

For years, Lilith had liked the idea of wearing diapers in her spare time, as a way to relax/cope with her mommy issues. Of course, ever since she started living at the Owl House, it's been hard to keep it a secret. Thankfully, she had kept this under wraps... until someone opened the door without knocking.