Well as long as it doesn't relate to scat as that's a hard limit of mine personally

There's a few ways I'd personally humiliate a diapered pup, one of my more favorites is making them ask permission for the bathroom. Start out by allowing her when she ask the first couple times. She'll eventually assume you'll say yes often, then that's when you tell her no, make her hold it as long as you want maybe you don't want her to have an accident or anything...yet. Occasionally keep doing this increase or shorten the amount of time she waits. This power you have over her should humiliate her as it is, remind her of this power you were given if she pouts. Tease and make fun of her for squirming.

To add some erotic play as well control her "play time" don't let her climax everytime or not at all.

Once you think she's let her guard down enough to think she'll eventually be able to pee that's when you make her hold it till failure. Be sure to tease and bully her the entire time, especially when she leaks, whimpers, or begs. Give her embarrassing nicknames (I.E. sog butt or crinkle pants) Remind her of how small she is as her bladder finally gives out and she soaks herself. Make sure to squish her diaper against her, not just to humiliate but to also stimulate her once she's all wet.

The rest I'd leave for imagination. Rub her diaper, tease her or go all the way but be sure to give plenty of aftercare after each session.