The woman approached Nottinghamshire Police in 2018 to report multiple sexual assaults in Nottinghamshire, committed against her when she was still at school.
Detectives began looking into a series of allegations against Julie Marshall, who was known as John Marshall at the time of the offences.
The 55-year-old declined to comment when interviewed by officers, but later admitted four counts of indecent assault against a girl under the age of 14 and two counts of indecency with a child.
Marshall, of Warbreck Drive, Blackpool, was jailed for 27 months by Judge Jacqueline Coe.
Marshall will also be added to the sex offenders’ register for ten years.
Detective Constable Stephen Dunn, of Nottinghamshire Police, said: “These offences may have happened many years ago but their impact on the victim have been profound.
"As with all offences of this nature, what matters is not how long ago something happened, but the fact that it happened at all.
“Nottinghamshire Police is committed to investigating all allegations and listening to the experiences of victims.
"We will always follow the evidence presented to us and take further action if we can.
“I am pleased that Marshall has now been punished for this offending and hope the sentence will provide some solace for the victim.”