She should have been in a classroom working towards her GCSE exams, making sure she achieves the grades she needs to study photography at college.

Instead after a gruelling three-day trial the teenager found herself in front of a judge being convicted of falsely claiming that she was raped last summer when she was just 15.

The case has caused alarm among anti-rape campaigners and legal experts who believe it is yet another example of the increasing readiness of the police and the Crown Prosecution Service to pursue women – or in this case a girl – who in their eyes falsely claim rape.

It has caused a rift in the tight-knit community in the Forest of Dean in Gloucestershire where the girl and boy still live half a mile apart. A court order means the young people cannot be identified but in the place where they live almost everyone knows who they are and even some of those who support the boy are questioning why the case went so far.

Both the girl and boy, who was 14 when he was accused, continue to suffer. His family say he receives "threats and abuse" and they worry for his safety. The girl's parents told the Guardian she hardly ever goes out, feels like she is a "prisoner in her own home" and fears she will become a real prisoner when she is sentenced for attempting to pervert the course of justice next month. "We're living in a nightmare right now," her mother said. "We can't believe it's worked out like this."

The saga began with a game of truth and dare at the boy's house on August bank holiday last year. The girl and a friend were invited up to the boy's bedroom. The boy was there with one of his close friends.

It is agreed that the 15-year-old girl had sex with the 14-year-old boy and then left with her friend.

The following Sunday the girl was with her friend at a church youth club. On a mobile phone she tapped in the message "I think I might be pregnant" and told her friend that she had been raped by the boy.

She said the same thing to her family and eight days after the incident went with her mother to the police station and made a complaint.

In her first police interview the girl said had been alone in the room with the boy. She said she had been a virgin, told him "no" when he touched her and tried to push him away but he raped her.

Next day she was interviewed again. She said she had been "too scared" to call out to her friends. Asked why she had not reported the attack sooner, she shook her head. "I was upset but I didn't show it," she said.

The boy was arrested. His version was very different. He said he had asked the girl if she had had sex before. She replied that she had not. He asked her if she wanted to and she told him "yes". Crucially, he said both the girl's friend and his male friend were in the room at the time.

His account was backed up by the girl's friend. She explained that the pair had the bed clothes over them so she could not see what was happening. But she said the girl had been quiet and she did not believe she had been raped.

When the 15-year-old girl was interviewed for a third time by the police, it was as a suspect rather than a victim. She conceded there were four of them in the room but insisted she told the boy to stop. "I didn't feel comfortable," she said. The girl said she had been whispering for him to stop. "I was scared," she told police. She said she had "frozen".

Before the case reached trial, the girl's defence team hoped to halt it by writing to the CPS's policy team asking for its opinion.

The issue was in the headlines at the time because of the high-profile case of "Sarah", who was convicted of perverting the course of justice after retracting a rape complaint. The CPS reacted to that case by announcing it was drafting guidance on what factors prosecutors should consider when deciding whether to charge someone with perverting the course of justice after a false or retracted rape allegation.

The director of public prosecutions, Keir Starmer, said he should be personally consulted before prosecutions such as Sarah's went ahead. But the Forest of Dean case did not reach Starmer's desk and was left in the hands of local prosecutors.

The trial of the girl, who had turned 16, took place at a youth court within the magistrates building at Cheltenham. When she was not in court the girl spent time in the main area with adults waiting for their cases to be heard, which her parents said had been a traumatic experience.

The prosecution said the girl had not been raped and knew her claim could lead to the boy going to jail. In her evidence the girl said she had lied to police about some of the details but maintained she had been raped.

The district judge, Joti Bopa Rai, accepted it was feasible the girl had "frozen" but highlighted the "odd circumstances" of how she had first spoken of the rape in the youth club. She also flagged up the evidence that the girl and the alleged attacker were seen holding hands after the alleged attack. The girl denies this happened.

The judge concluded this week that the girl consented to sex. It was possible, she added, that the girl had lied because she feared she was pregnant or to "cover her tracks". "That lie grew bigger and bigger and bigger." The judge said she appreciated that the defendant was young but said she came across as intelligent. "She knew the consequence of this lie," the judge said.

Wearing a favourite purple sweater, her hair held back by a bright pink band, the girl heard that "all options" would be considered when she was sentenced.

At the girl's home this week, a neat red brick house on a modern housing estate, her parents said they still believed her account. Her mother said the experience had made the girl, who is now 16, withdrawn and reluctant to go out.

The girl, who has never been in trouble with the police before, has to catch the bus to school with youngsters who know the details of the case. "She gets it on the bus and at school," said her mother. "It's affected her school grades. This sort of experience would put people off going to report anything. She went to the police as a victim and suddenly turned into the accused."

Others in the community question the prosecution. The mother of the other boy who was in the bedroom gave evidence against the girl. "But I don't think it should have gone to court," she said. "There must have been a better way to deal with it."

Her son, a shy 15-year-old, also had to give evidence against the girl. "It was scary," he said. "I really didn't want to do it." He, too, has become more withdrawn and reluctant to go out.

Campaigners strongly criticised the decision to prosecute the girl and said such cases put women off reporting rape.

An estimated 95% of the rapes that take place in the UK are never reported. Only 6.5% of reported rapes in England and Wales result in a conviction on the charge of rape.

Lisa Longstaff, of Women Against Rape, said: "We are particularly horrified by the fact that in this case she is so young. The criminal justice system and the tabloids have seized on these prosecutions to undermine rape victims and distract from the huge number of rapes that are never prosecuted.

"They reinforce the sexist view that women commonly lie about rape. Every prosecution puts women who have been raped off reporting it. As a result more rapists are free to rape again. There was no need to prosecute this girl.

"We ask the DPP, when over 90% of rapists go free, is prosecuting a 16-year-old justice? It is perverse. It doesn't protect innocent men. It is not necessary to prosecute women in order to protect men from false allegations. A thorough investigation should be enough to establish the facts of any case."

Clare McGlynn, professor of law at Durham University, said the case was extremely troubling. "It seems that the veracity of this rape allegation was tested not in a trial of the accused but in a trial of the complainant before a district judge, not a jury.

"In most of the reported cases of false allegations of rape leading to convictions for perverting the course of justice, there has been an admission from the woman or very clear, irrefutable, evidence that she was lying. However, here we have a young girl maintaining that she was raped. The fact that she changed her story is in no way evidence of lying but indeed is common in some victims, especially the young, as they may be confused or reluctant to tell the whole story."

David Wilson, professor of criminology at Birmingham City University, said the girl's age should have been taken into account. "We wouldn't allow this girl to have driven a car, buy alcohol, cigarettes, or even buy a pet, but here we are prosecuting her as if her age is not relevant. It seems to fit a pattern in our culture whereby we want children to be older much younger than we did a generation ago – especially when it comes to the law."

The police insist they were right to pursue the girl, partly to help restore the boy's reputation.

Forest of Dean Detective Sergeant Mark Stenhouse said: "We take all rape allegations extremely seriously and thoroughly investigate any that are brought to our attention.

"While cases of perverting the course of justice are rare and charges are not often brought against youngsters, this was an obvious case. The young girl's account of what happened to her was contradicted by two eyewitnesses who were present when the assault was alleged to have happened and other strong evidence.

"We are very conscious of the needs of youngsters which is why we also had to consider the impact on the 14-year-old boy who had been accused. The impact on his life has been terrible and the case has caused great distress to him and his family. With his reputation cleared we hope he can go on to rebuild his life and get over this period."

A CPS spokesperson said it had carefully considered whether it was in the public interest to prosecute the girl. "We concluded it was as she made an extremely serious allegation which was strongly undermined by the evidence, including witness statements. And her victim suffered serious repercussions as people he knew believed he was a rapist, and treated him as such."

The spokesperson added that the CPS was continuing to draft its guidance on how cases like this one should be handled. "We will seek the views of charities and other groups before finalising the guidance," she said.

The boy's parents told the Guardian they believed the trial had helped. "She put us through hell," his father said. "My son has had threats and abuse from other kids. He tends to keep himself to himself more and when he does go out we're worried about him.

"It was terrible when he was arrested. His mum was in hysterics. All we wanted was for her to admit it didn't happen but she never has. The case has given us some sort of closure." Would he welcome a custodial sentence for the girl? "If it stops someone else doing the same thing, yes."