Gemma Barker wore baggy clothes to cover her figure and baseball caps to shield her face and spent seven months in relationships with girls of 15 and 16.
She walked and talked like a boy and managed to fool both the girls, who went to the same school as her, and police who arrested her over the romps.
It was only when she removed her clothes in the cells that police discovered her true identity.
Barker, now 20, admitted sexual assault and fraud at Guildford crown court yesterday.
She created fake Facebook characters – Aaron Lampard, Connor McCormack and Luke Jones – to lure her victims after they told her about their ideal boyfriends.
When she’d earned their trust, she disguised herself as boys to meet them for kissing, cuddling and petting sessions at their houses and to meet their families.
Barker wore different clothes for each character and her disguises only begun to unravel when her victims, who knew each other, became suspicious that they were dating the same boy.
Prosecutor Ruby Selva said: “Having befriended the victims she disguised herself as various 16-year-old boys for the sole purpose of having sexual relationships with them.”
The court also heard that Barker had tried to contact girls as young as 13 and 14 online, four years before.
Judge Peter Moss said Barker was “mean and manipulative” and warned that she could face jail.
Barker was ordered to sign the sexual offenders’ register.
Her older victim called her a “compulsive liar”.
The girl, who cannot be named, said: “She went to extremes. She lied about her family dying. I can’t remember the amount of people she told me died.”