I actually like it better if it's a mechanical process. Not magic or anything like that. If someone covers the girl with epoxy resin and it gets hard. Or liquid gold (I know that's painful). Not the human being is transformed, but the human being receives an envelope!
I'm not into encasement, a living person trapped inside a hard outer shell, threatened by starvation, suffocation and other horrible things, naw...
I think it stems from a childhood trauma. I was a toddler and crawled in a trunk during hide and seek, shut the lid and one of the latches snapped shut. I screamed, hollered and struggled trying to open it. Luckily after a dozen seconds or so the lid twisted on one side and the latch fell loose and I was free. Shook me to my soul.
If I had been turned into an immortal inanimate object that didn't need air, food or water and was locked in a trunk I wouldn't be upset.
I hide the transition / transformation in my thoughts!