Gemma Hill, 33, discussed with boyfriend, Stephen Arnopp via messages on how he would rape the girl. Asides planning the rape of a girl less than 13, they also plotted the rape of a nine-year-old girl.
Judge Marie Catterson said Hill had an "extremely low" IQ. She added that the victim had suffered "incalculable" long-terms effects likely to be "difficult and profound" after the pair admitted all charges against them.
Sentencing Hill, Judge Catterson said: "You were evasive, pretending you knew nothing."
Catterson made a Sexual Harm Prevention Order banning Hill and Arnopp from contacting the victims and from living in a house or having any unsupervised contact with girls under the age of 18.
Both defendants pleaded guilty to the charges against them. Arnopp was given two concurrent 40-month sentences for two counts of conspiracy to commit sexual activity with a child under 13 and was jailed for eight years consecutively for two counts of raping a child under 13.
He was also sentenced to one count of inciting and one count of causing a child to engage in sexual activity, receiving four months concurrent to his other sentences and received eight months, also concurrent, for sexual activity with a child under 13.
Hill received two concurrent four and a half-year sentences for two counts of conspiracy to commit sexual activity with a child under 13 and a consecutive 18-month sentence for cruelty to a person under 16.