Wow....I first saw your post on Sunday so I couldn't post back then, all I could do was send a thanks, but I have to say that was a great point! I think every female has a combination of both of those powers in her nature, each individual to different degrees....and I'm not just talking about the female characters in SK's novels although there are plenty of examples!
I, too, thought that sex scene was so beautifully and thoughtfully written that it didn't seem perverted or wrong to me at all. And while I definitely agree with you about Bev's father behaving violently towards her because he was afraid of her growing up and afraid of her growing power as a woman, I think there was a little more to it than that. I'm pretty sure it was because he was afraid of his own feelings of sexual attraction towards her as she grew to womanhood; he felt that those desires were evil, and that would have given rise to the irrational thought that she was evil for arousing those desires and needed to be punished. There were two telling scenes in the book that support my theory; Bev's mother asking her, "Does your father ever touch you?", and the scene after she returns to Derry as a grown-up and confronts the witch who morphs into her father, who tells her, "I beat you up because I wanted to **** you". The former tells us that the mother sensed those undercurrents in the relationship between Bev and her dad, the latter was It voicing the fears in Bev's own mind. And we don't see any evidence in the book of Bev's father beating his wife as well, which is often the case with abusive men; even though he could have been abusive to his wife in other more subtle ways, he felt more intensely hostile towards his daughter.