Jordan Lightfoot was found guilty of having sex with the boy in her home in the summer of 2016.
The then-19-year-old was exposed after the boy’s shocked mother contacted police when she read messages between the two on his phone.
Jo Maxwell, prosecuting, said text messages between Lightfoot and the 13-year-old "made it obvious she was in control of the relationship."
Judge Hale said it happened during a troubled period of her life, living on her own.
"You became involved with a group of lads, people who were prepared to befriend you, and you were prepared to befriend them,” he told Mold crown court.
The incident was the schoolboy’s first experience.
Lightfoot, now 21, denied sexual activity with the boy and also to sexually touching a lad of 15 and inciting him to engage in sexual activity, but was convicted earlier this month.
Sentencing her, the judge said: “On these two occasions you engaged in a brief sexual relationship with both of them.
“The 15-year-old had become obsessed with her - and that's always the risk.
"There is a disparity of age, they were vulnerable because they were even less equipped than you to deal with the emotional relationships involved,” he said.
Lightfoot, from Rhyl, north Wales, was sentenced to 18 months in prison, suspended for two years, and banned from contacting boys aged between 11 and 16 unless inadvertent or with consent of parents who know about the conviction.
Lightfoot, who is now the mother of a baby, was warned by the judge: "No teenage lads around for parties or anything like that."
She will now be on the sex offenders register for ten years.
