I'd suggest that out of 3000 people that have engaged in criminal sexual conduct with a minor, it's closer to 120 than 12 (and possibly closer to 1200) that are female. And they don't even have to sweep female perps under the rug for that statistic, just punish them less severely than male perps (since the quoted statistic is based on incarcerations and not offense rates.)

As for a better statistic to use, I'd start off with convicted offenders and see how that compares.