Charlotte was just six when, after playing outside together, eight-year-old Sarah Payne vanished from a country lane near their grandparents' house in July 2000.
A nationwide search was launched but, tragically, Sarah was found dead 16 days later in a field in Pulborough – 15 miles from where she vanished in Kingston Gorse, West Sussex.
Over a year later, paedophile Roy Whiting, 56, was convicted of her abduction and murder and sentenced to life imprisonment.
After the trial it was revealed Whiting had previously been convicted of abducting and indecently assaulting another eight-year-old girl – which led to the introduction of Sarah's Law.
Now, 15 years on, Charlotte insists she'll never let her sister be forgotten.
Charlotte, a retail assistant who lives with her mum and younger sister, Ellie, 11, in Hersham, Surrey – just a stone's throw away from Sarah’s childhood home – says: “To everyone else, Sarah is the sweet little girl smiling in her school uniform in the newspaper pictures.
"But, to me, she’s still my sister and best friend. I never want her to be forgotten.
“She was always lovely and we were really close.
"I was naughtier than her, but she was mischievous too.
"Once mum had a party and we snuck downstairs in the morning and ate all the leftover food, we’d never been so full!
“We shared a room, and I remember us chatting, sitting on her bed. She’d be clutching her teddy bear and a red blanket – I’ve kept them and will always treasure them.
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“I’m proud to be her sister. What happened was horrific, but Sarah’s Law has potentially saved so many lives.
"It’s allowed me to find some peace, because I was angry for a long time.
“A lot of people say I have the same eyes as Sarah because they’re dark brown. I can see the similarities but I don’t feel I’m living in her shadow."
To read more of Charlotte's touching story, read this week's Closer magazine