None of those are cases of sexuality chosen by the girl because she wants it for its own sake.
girls being married while in their single digits, and later recounting their marriage as being a happy one
That certainly could include such things as the marriage not being consummated right away, other aspects of the marriage outweighing unpleasant sex, sex being unpleasant at first but pleasant as they got older...
ancient Greeks who believed that a virgin would die if she began menstruating because the hymen would trap the blood - which implies that they did not have many virgins old enough to menstruate
Even if true, it certainly doesn't imply anything to do with a girl's pleasure!
other cultures where even recent history has shown a good deal of social acceptance of child sexuality
There has been acceptance of "child sexuality" in the sense of "not getting totally upset at men for having sex with children", but not in the sense of "the prepubescent being actively interested in sex with an adult".
we have plenty of accounts of girls who wanted such a relationship with an older man
A sexual relationship for its own sake, in the moment? Usually they wanted to get married -- nabbing a high status man might well be worth it if the cost was just some unpleasant early sex, etc.