The US X Factor judge wore the metallic number on last night's show (21 November) while Ella wore hers to the Kardashian Kollection for Dorothy Perkins launch.
The best bit? Their metallic seam shift dress is straight out of Topshop, priced at £55.
Snap yours up fast as it won't hang around for long now these two beauties have rocked it!
Both Demi and Ella paired it with opaque tights and black heels for a leg-lengthening effect.
Demi went for minimal accessories, a simple ponytail and matching silver nails.
Ella added a jacket, £59, and clutch bag, £25, both from Dorothy Perkins, while her locks were worn in a sky-high bun with plait detail.
It's the ultimate US versus UK fashion face-off!
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