how rare it is that transwomen sexually abuse biological women? Is it more common than the abuse of women by other biological women?
From my understanding based on a Swedish study, transwomen are as likely as men to commit all types of abuse, including violent and sexual abuse. (Men commit 98% of all sex crime and 80% of all violent crime, TW will be as likely as the next man to be an offender, obviously because NAMALT it's not a huge percentage of men overall). Statistically, TW will be far more likely to abuse a woman, than a woman abuse a woman.
However, Fair play for Women released data under the freedom of information act, that 41% of all transwomen in prison are in prison for sex offenses, (eg pedophilia, sex assault, downloading illegal porn, rape, voyeurism etc). This is actually much higher than the non-transgender male prison population, of which about 19% prisoners are inside for sex offenses. So to say TW commit (sex) crime at the same rate as males is something worthy of more research.
It is safe to say that statistically TW as a percentage of the population will commit sex crime against women at a far higher frequently than women will commit crime against women, but because the population of TW is low, the individual occurrences will be very low too, so it depends how you're looking at the statistics.