"She wouldn't listen and she would just do whatever she wanted anyway".
Charlotte Jones's little sister Georgia died after taking two ecstasy pills at Mutiny Festival in Portsmouth in May.
She was 18 years old.
Charlotte, who's 23, admits to knowing Georgia had tried drugs in the past and says she warned her against taking them.
"She was a party girl who always wanted to have fun, but I never thought anything bad would happen," Charlotte tells Radio 1 Newsbeat.
"I ended up saying be careful but knew what she was going to do. She told us, she was an open book."
Tommy Cowan, aged 20, also died on the first day of the Mutiny Festival. His dad has since warned others about the dangers of taking drugs.
Five people were arrested during the police investigation at the time, but were released without charge.
Hampshire Police told Newsbeat that the case is "ongoing" and that four people remain under investigation.
The last time Charlotte saw Georgia, they went on a country drive in Hampshire, a couple of days before the Mutiny Festival.
"She liked playing Eminem. It was just me and her and it was nice. I'm actually glad I have that memory together with her.
"I do that drive by myself sometimes, because we all have our little moments. I'll do our drive and put on our music. It's something that keeps me sane."
Charlotte has found life hard since her sister's death.
When she found out what happened she was stunned. "I just dropped to the floor and everything went dark," she says.
Now Charlotte and her mum Janine Milburn, 41, have started a petition calling for drugs testing at festivals.
"It would mean Georgia didn't die for nothing," says Charlotte.
Janine says she believes Georgia's life could have been saved if she'd known what was in the drugs she was taking.
Only since her death has her mum found out she'd taken ecstasy in the past.
"I believe every festival should have the front-of-house testing so people can find out what dose they are taking," she says. "A lot of people would change their mind once they know what is in it."
Charity The Loop, which tests drugs for potency and content has tried testing at festivals across the UK.
But the government says its message is "no illegal drug taking is safe".
Not only is Janine dealing with the grief of losing her daughter, but she's also had to deal with online trolls.
"I've had a lot of hate since Georgia died. She wasn't a drug addict, she wasn't out of her face. She worked hard, she was a normal teenager. People have been really nasty."
Janine says she has had "lots" of these messages. "I'm strong enough to ignore it," she says.