Keeley Houghton, 18, wrote in a post that she would kill Emily Moore, also 18, whom she had bullied for four years after meeting at school.
On her Facebook page on July 12, Houghton wrote: "Keeley is going to murder the bitch [Moore]. She is an actress. What a fucking liberty. Emily Fuckhead Moore."
Two days before the threat was made, Houghton had approached Moore in a local pub. When Moore threatened to call the police, Houghton told her: "I'll give you something to ring the police about."
After pleading guilty to harassment, Houghton, from Worcestershire, was sentenced to three months in a young offenders' institute and given a five-year restraining order.
Houghton is banned from contacting Moore, or commenting about her on any social networking website during that time.
She already had two previous convictions for her vendetta against Moore -- one for physically assaulting her as she walked home and another for causing criminal damage to her home.
District judge Bruce Morgan told Houghton: "Since Emily Moore was 14 you have waged compelling threats and violent abuse towards her.
"Bullies are by their nature cowards, in school and society. The evil, odious effects of being bullied stay with you for life. On this day you did an act of gratuitous nastiness to satisfy your own twisted nature."
People have previously been jailed for harassment and stalking on social networking sites but Houghton is the first to be jailed for bullying via the internet.
Last year a US woman accused of pretending to be a teenage boy on MySpace and driving a 13-year-old girl to suicide after sending her cruel messages .
Prosecutors said that Lori Drew, a 49-year-old from Missouri, created a fake persona of a 16-year-old boy called "Josh Evans" to flirt with neighbour Megan Meier and lure her into an online romance, before abruptly ending it, saying the world would be a better place without her.
Just hours after "Josh" abruptly ended the relationship in October 2006, Meier hanged herself in her bedroom, completely unaware that "Josh" did not exist. She died the following day.
, however in July this year a federal judge overturned the guilty verdicts.
.jpg)
.jpg)