It depends on what you mean by very rarely. According to the Center for Sex Offender Management, an estimated 1.6 million men and 1.5 million women are sexually abused by women when they were children.
According to Law Professor Kay Levine, it is estimated that 1.5 million girls and 1.1 million boys are victims of female sexual abuse in the United States.
The numbers vary depending on the study 600+ studies on this subject and the above information came from http://www.female-offenders.com/
There are women offenders abusing girls too. Elsewhere I've heard women say, "they betrayed their own sex" in raping them. Never put in those words myself about my male rapist (his wife raped me too). Male offenders are just mored derided than women offenders. Women offenders also get more "compassion" or the boys aren't believed or called lucky if they are say, 14-up.
Too many guys say, "Dude, I'd have killed for that in high school. Where were those teachers when I was in high school? Lucky dude." Saw a lot of those comments recently when the Cincinnati Bengals cheerleader got arrested for allegedly having sex with a 16 year old student.
One thing I wonder since 50% of child rape is violent vs. like 30-35% of adult rape according to statistics, which gender is more violent? It's all violent since against someone's will.
Is it the lack of violence with half of offenders, male or female, why it's such a damn problem for victims to grasp?
I didn't know for 23 years. Was mad at the male not the female perp. I blamed the male perp for it not her even though she participated and did most of the rape. Guess because I suffocated on his penis. Yeah, disgusting. But, if I could've found them, both would've gotten killed over it slowly, with lots of pain.