Chloe Allan, 15, began Tweeting Sam 18 months ago, when she saw him performing with another band District3.
He was voted off X-Factor last year and Chloe - who hopes to go into entertainment PR - helped him get gigs and radio interviews in Scotland.
But since his rise to stardom, she has been subjected to increasingly frightening abuse - including death threats - on the social networking site.
Chloe, from Aberdeenshire, said: "I am upset and scared all the time. It all started totally out of the blue. But it has been getting worse. We keep blocking the accounts but whoever it is just keeps setting them up again.
"They say things like we know when you are coming to Glasgow. We know what train you are getting. We are going to be there and will kill you when you arrive."
Her mum Julie, 40, has tried to get Twitter bosses to stop the death threats, but has claims they 'don't consider it an emergency' and has vowed to take them to court.
She said: "Chloe has been receiving these awful messages, death threats, every night for a year-and-a-half. Chloe will block the abusive account but then another one is made the same day.
"It's absolutely ludicrous. Twitter need to start taking some responsibility for this. Some of these messages that are coming through to Chloe say 'I'm untouchable, I can't get caught'.
"I'm willing to battle this no matter how much it takes, no matter how long it takes. They have been posting stuff about my house and how they're going to come over, so for Twitter to say that's not an emergency is a kick in the teeth."
Julie does not want to completely take Chloe off social networking because she says it is a necessity for connecting with her friends.
A police spokesman told Mail Online that investigations are ongoing. Twitter said the company could not discuss individual accounts for 'privacy and security reasons', but added that it has established processes in place for working with law enforcement, and makes information and advice available for users who feel they are the target of online abuse.
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