Since they condemned masturbation in a '59 QFR, I doubt they figured it was OK in this one. (But they change their minds so much, who knows?) The point of them saying " It is high time for girls to understand the make-up of their bodies and its functions" has to do with the previous analogy - namely, that girls should realize that when they're ovulating, they are inclined to act like horny cows ready to jump any old bull's bones. The point is also made that it's up to the girl to maintain her chastity, as well as that of the boy: " Ordinarily the male or bull would not think of approaching the female or cow for sex purposes. If he did approach he would not receive a hearty welcome, but, rather, he might be gored by the cow’s horns. There is no petting or sex relations between bull and cow permitted, because the female is not in physical condition to breed. The bull seems to understand this and keeps in his own place."
Therefore, girls need to do everything in their power to make sure they live through Armageddon by following the Org's advice: to be a "clean, happy wife," the mother of "legitimate children". If she does this, she'll get to live happily ever after in "the new world of righteousness" without all those pesky sexual urges.