"But come onnn, it's collldd." Amanda pouts, standing up. As she does so, however, she feels an unnverving sensation in her diaper.
You make a few loud sniffs.
"...did you just..."
You watch as Amanda's expression freezes up, and a bright red blush covers her face.
"Amanda, did you mess yourself?" You ask, looking around her and observing the backside of her diaper.
"Oh goddd...." She groans. "I'm so sorry you have to see me like this..."
"Hey, don't worry about it. You can just clean yourself up and it won't be an issue anymore, yeah?" You put a hand on her shoulder.
"Y-yeah." She gets a bit of a tickle from your hand.
"Let me just..." she grabs the package of diaper and wipes and powder, "get to the bathroom so I..."
"Hey wait." You grab her wrist. "I want to watch."
"...what? Are you sure?" She asks, confusedly.
"Yes I'm sure. I just saw you clean yourself out of a wet diaper and didn't mind at all, so it would only make sense that I could watch you clean yourself out of a... dirty diaper and not be bothered by that either, right?"
"...yeah I guess so..."
Amanda takes form in the center of the living room. She bends down to arrange everything, much to her disturbtion, because any movement she makes with her legs causes her mess to spread and supplant itself against her in a manner that makes her cringe.
She lays down, opens her diaper and quickly begins to wipe herself. As you watch intently, you realize that she has no intention of changing into another diaper when she's done cleaning herself (presumably, she intends to hit the shower once this wiping has dealt with the majority of the mess). One quick command will fix that.
~You will change into another diaper once you are finished wiping.~
You watch as she actually puts that powder to use on herself, and tapes herself up into another diaper--her third diaper so far.
"Hey..." you say, "why did you put on another diaper?"
"Oh, that?" She thinks about it as she throws her dirty diaper away and washes her hands. "I dunno, I just did."
This once again affirms that if you command an action without a stated purpose, the victim will not understand the logic of their own action.