When you imagine Devil, what do you think he looks like? A scary large red beast with hooves, goat legs, horns, and a tail? Not exactly.
When you think of the devil, you think of him being scary, but he's not really. The devil seduces you into sinning, if he's scary then you're less likely to fall under his spell.
But if he's flawless, beautiful, then you'll think more about sinning.
And that's the case for poor little innocent Kelly. Drawn in by the looks of the devil, disguised as a mere angel. When she realizes the work of the devil, its already to late.