An 18-year-old woman has been jailed for three years on the grounds of obtaining the sexual consent of another woman “by fraud” because the victim thought she was male.

Justine McNally admitted six counts of sexual assault by penetration at Wood Green Crown Court in north London yesterday. She was placed on the Sex Offenders’ Register for life and ordered not to contact the victim and her mother.

The court heard McNally, who was 17 at the time, wore “Goth” clothing and persuaded the victim, then aged 16, to have sex with her.

They had previously met online when they were 12 and 13.

During the period, McNally used the name of “Scott” as an identity.

The secret was exposed when a family friend McNally was staying with discovered a strap-on sex toy and bra in her backpack. The victim’s mother then told her daughter: “You do know Scott is actually a girl?”

The mother and daughter then confronted McNally, who produced a picture on Facebook of her dressed in pink clothing and heels.

McNally said she wanted to have gender confirmation treatment in order to continue the relationship – but the victim’s mother contacted the police.

Judge James Patrick said a prison sentence was the only option available because of the damaged caused to the victim.

Jailing the defendant for three years, Judge Patrick said: “She had her first sexual experience with you, and you abused her trust so badly she finds it difficult to trust other people”.

“It was selfish and callous behaviour – a grave abuse of trust of her, her family and friends through your behaviour over a period of years.”

Prosecutor David Markham said of McNally: “She obtained consent to physical intimacy between them by fraud.”

Keith Thomas, for the defence, described the case as a peculiar and extraordinary one”.

He said McNally had “an unhappy upbringing” and was confused about her gender identity.