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Contostavlos, who was celebrating her acts Jade Ellis, Ella Henderson and Lucy Spraggan getting through to the next round, wore a strapless metallic green dress as she arrived at Aura nightclub.
The star was joined by James Arthur - who was surrounded by female fans - and JLS, celebrating their performance of new single 'Hottest Girl in the World' on the ITV show yesterday evening.
Meanwhile, Louis Walsh was greeted outside C restaurant in Mayfair by his number one fan, who wore the mentor's face on her underwear.
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