Poor Cadance. Despite being 18, she still wears diapers and wets them but thankfully, Celestia understands and wets hers so that she doesn’t feel alone.
 
Celestia comes to check on Cadance before they o to bed and noticed Cadance’s sudden turn to her while covering her somewhat big diaper bulge from her pyjama bottoms with both her hands from looking down before she entered her room. Celestia looking concerned walks over to her and asks why she looks so nervous & Cadance then pulls down her bottoms revealing her wet pullup.  
Cadance with tears coming down her face I’m sorry, auntie, I still wear them because this keeps happening. I’m 18 and I shouldn’t be having to wear these but it just keeps happening to me.  
Celestia: hugs the crying Cadance tightly, gently stroking her head it’s ok, there’s no need to apologise, you didn’t do anything wrong. You know, I wear diapers too.  
Cadance: still with tears down her face but her eyes shoot wide open what? You do?  
Celestia: with a warm and comforting smile on her face, she opens her bathrobe revealing her wet swollen diaper I have very busy days and sometimes, have no time to use the bathroom so I wear these to save time.  
Cadance: starting to cheer up a bit and smiling Wow. I had no idea.  
Celestia puts her hand on Cadance’s shoulder Don’t you worry, my dear. these things happen to a lot of people.  
Cadance: dries her tears & starts to smile Thank you auntie, that makes me feel less embarrassed. Can we keep this a secret between us?  
Celestia: giving another warm smile sure thing, I won’t tell anyone gives her another hug  
Cadance: hugs her back Oh, thank you, auntie, you’re the best.  
Celestia: while hugging Cadance, wets her diaper a little more. oooh, i just wet myself a little more  
they both laugh a little, and Cadance looks at Celestia’s diaper & then down to her pullup just out of curiosity  
Cadance: Wow, yours is so much bigger than mine.  
Celestia: giggles Well, that’s what a long busy day as princess does to you.
 
Celesta: Did you want to sleep with me tonight?  
Cadance: accepts happily That’d be great. Thank you.  
Celestia: smiles as Cadance cheerfully walks over to her You’re welcome, I think you could do with some comfort from a diaper wearing princess.  
so Cadance follows Celestia into her bedroom, get under the sheets & spoon as they sleep while taking comfort in knowing they’re both safe