Most rapists were subjected to some form of sexual abuse in childhood. A startling amount is perpetrated by females. Peer-reviewed studies conclude that between 60% to 80% of "rapists, sex offenders and sexually aggressive men" were sexually abused by a female. [...] According to a 2004 U.S. Department of Education mass study of university students, 57% of students reporting child sexual abuse cited a male offender, and 42% reported a female offender. Interestingly, 65% of the survivors of female abuse who opened up to a therapist, doctor or other professional were not believed on their first disclosure. Overall, 86% of those who tried to tell anyone at all about their experiences were not believed. According to a 1996 report from the National Center on Child Abuse and Neglect (NCCAN), about 25% of child sexual abuse is committed by women, but that figure may be low, because survivors are far more conflicted and shamed in admitting abuse by their mothers than by fathers. In one study of 17,337 survivors of childhood sexual abuse, 23% reported a female-only perpetrator and 22% reported both male and female. A U.S. Department of Justice report finds that, in 2008, 95% of all youths reporting sexual misconduct by staff member in state juvenile facilities said their victimization experiences included victimization by female personnel, who made up 42% of the staff. [...] One study found 8% of female perpetrators were teachers and 23% were babysitters.
Based on what one could read on reddit, sources for the stats are here and here. Also.