The idea of the 21-year-old doing the challenge came about during a night out with friends at the weekend.
“It was something nobody else had done,” she said. “It was just harmless fun. Everybody seems to find it really funny.
“I didn’t realise how far it would spread and how many people would see it. I have had messages from as far as Australia and people are calling me a legend.”
The video has been viewed by thousands of people and although she has received a lot of messages of support, there have been some negative comments.
Miss Ralph, who said she donated £20 to charity after completing the challenge, added: “Harvey was always safe. I compete at county level and I have been around horses since I was six. I was always in control.”
The craze, which involves downing a drink at the end of the challenge, has been linked to the death of an Irish teenager who jumped into a river after excessive drinking and in a separate incident a 22-year-old man was found dead in his home, also in Ireland.
Parents of students at Richmond School have been warned about the dangers of NekNominations by deputy head teacher Jenna Potter.
In an email headed "potential student welfare concern", Ms Potter wrote: "We would ask you to be vigilant as a parent/carer to ensure your son/daughter is not involved in any inappropriate and potentially dangerous behaviour as part of the above campaign."
Helen Goodman, MP for Bishop Auckland, has also condemned the stunts.
She said: “I think encouraging this kind of behaviour on social media sites is totally irresponsible.
“Today Facebook is ten. I really think it is time for the executives of the company to grow up.”
Chief Inspector Sue Robinson, of Durham Police, said they were aware of who was involved and would be asking them to attend the police station at the earliest opportunity.
“On Monday afternoon police were called by staff at the Tesco store reporting a number of young women had been in the premises, with one of them riding a horse,” she said.
“They allegedly threatened a member of staff before leaving a few minutes later.
“At this stage we are trying to establish what criminal offences might have been committed and discussions have taken place with the RSPCA in regards to the welfare of the horse.
“It goes without saying this was a senseless and foolish thing to do. There were a number of shoppers in the store at the time and it is fortunate no-one was hurt.”
A spokeswoman for Tesco said: “We are aware of the incident and the police are investigating.”
* Did you see the incident in Tesco, call our Newsdesk on 01325-505065.
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