Inflatable Zoe

In a flash of purple light your sister transforms into a cheap inflatable sex doll. Her beautiful body becoming a crude plastic approximation of her human form. Her face appears painted on and her hair has turned to coarse nylon. Her mouth and pussy gape open in obscene ovals showing the plastic sleeves inside them. The rest of her body is similarly basic, her breasts and limbs not much more than shaped balloons joined to her torso by rough glued seams.

On the plus side she weighs next to nothing like this and if you popped the valve on her back she'd probably pack down nice and flat for easy storage.

There's something appealing about that thought. Deflating her and stuffing her in a draw for a few hours would definitely reinforce the idea that she's your property. But you're also curious how being like this feels for her and you'll have to restore her to ask her about it...