What YouTube superstar Zoella reveals about teenage girls (and how it's left her smiling all the way to the bank), writes SARAH VINE

Her book hasn't even gone on sale yet, and — thanks to the scale of pre-orders — already it's number three on the Amazon Bestseller chart.

She has more than six million subscribers on YouTube, where her video blogs — 'vlogs' — attract 12 million hits a month. She has her own range of bath and beauty products, which sold out within ten hours of hitting the shelves at Superdrug.

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