Tulisa Contostavlos has told a court that a celebrity blogger she is accused of assaulting had a "strange obsession" with her.
Celebrity writer Savvas Morgan said he suffered swelling to the eye after an alleged incident involving the ex-N-Dubz star and former X-Factor judge at the V Festival in Chelmsford, Essex, last year.
Tulisa has denied an assault charge linked to the alleged altercation last August. The 25-year-old is on trial at Chelmsford Magistrates' Court with her assistant Gareth Varey, who is accused of threatening behaviour, which he also denies.
Giving evidence, the singer described the incident as nothing more than a "playground slanging match" which had been used as part of Mr Morgan's "vendetta" against her.
She added: "This is my life on the line, my livelihood.
"I cannot believe it has been taken to this point and I'm standing here today."
Tulisa, who is nicknamed The Female Boss, said Mr Morgan had attempted to follow her back to her Winnebago at the festival after she had watched a performance by Beyonce when she asked him to stop.
"There was a point that I swore," she added.
"At the start I was trying to be calm but this approach did not seem to work with him as he got more heated."
The singer, who claimed she kept her hands behind her back during the confrontation, described how Mr Morgan called her "a slag, a whore and a nobody" and made reference to her mother's mental illness.
Detective Sergeant Amanda White told the court stars who witnessed the incident, including singer and rapper Misha B, Sugababes singer Mutya Buena, singer Alexandra Burke and rapper Wretch 32, had all been asked to give police statements through their representatives. No statements were forthcoming.
Giving evidence wearing a black suit and black polo neck jumper, Tulisa was asked by her barrister Jeremy Dein QC about a sex tape of her which was leaked to the press.
She added: "A couple of details made me believe he (Mr Morgan) was involved a lot more than he made out."
Describing the publication of the sex tape, she went on: "I was horrified - it was one of the worst times of my life.
"An ex-boyfriend had taken what was supposed to be private footage of us and many years later tried to sell it and put it online."
But she said she held no grudge against Mr Morgan: "There were many people involved.
"I feel that some of the things he was doing were very mean, I didn't like the man, but he was one of many people who had issues or dramas with me.
"It's part of my life and I'm pretty used to it by now."
She said Mr Morgan's campaign against her dated back to an incident in the Whisky Mist nightclub in Mayfair, London.
Tulisa said she had been filming for The X Factor with groups Little Mix and The Risk when Mr Morgan tried to join their table.
She said Chloe Green, star of Made in Chelsea and daughter of Sir Philip Green, was with Mr Morgan.
"When I saw these people I had never seen before I alerted the security guard that we were filming and asked that they be removed from the table," she added.
Prosecutor Matthew McNiff quoted part of her autobiography, Honest, in which she describes how she suspected Ms Green had an affair with fellow N-Dubz member and former boyfriend Fazer.
She said: "This came after the Whisky Mist incident."
She outlined other incidents involving Mr Morgan, including an argument with him at the luxury Mondrian hotel in Los Angeles, and said at times he behaved like a stalker.
"For the past two years he has been causing drama in my life as much as he can and has been following me to hotels across the world," Tulisa added.
"It is something I have learnt to deal with."
In his statement, Varey, 28, said neither he nor Tulisa had attacked Morgan.
"Neither of us would have done this as it was exactly the reaction he was looking for so he could make unfounded allegations against her and me," he added.
Yesterday Mr Morgan told District Judge Angus Hamilton that Tulisa raised her fists in the air and was swinging her arms.
"Everyone was jumping around trying to get at me, there was a lot going on," he said.
Prosecutor Matthew McNiff said the incident happened at 12.30am on August 18 as Mr Morgan was about to leave. He said Tulisa accused Mr Morgan of stalking her, and swore at him.
Tulisa and Varey are both on unconditional bail.
Varey told the court that the Festival was the first time Tulisa had appeared in public since a front page story following a newspaper investigation into another matter.
"The eyes of the world were on her and every photographer wanted a picture of Tulisa," he added.
Describing the confrontation, he said Mr Morgan had raised his voice and been aggressive in an intimidating manner.
But he said neither he nor Tulisa had attacked him and the first he knew about the claim was when he was contacted by journalists the following day.
"Vas (Mr Morgan) is doing it to get his name in the paper," he added.
Varey said he had accepted a police caution for a previous incident in which he sent an email threatening to kill the personal assistant of Sun on Sunday investigative reporter, Mazher Mahmood, who is known as the Fake Sheikh.
A third person, Jacqueline Moore, 39, from Manchester, has admitted a public order offence in connection with the incident. She was fined £130 yesterday.
The trial will not sit on Wednesday or Thursday and is expected to conclude on Friday.