Min has a viewing that Rand needs Moiraine in order to succeed, but unfortunately Min believes that Moiraine is "dead and gone". When she is thinking about her confusion over the one viewing she had that didn't come true, she is actually commenting on the one where Thom and Moiraine end up together. Min didn't see "Rand succeeding" in her vision (that would kinda make the suspense of the series pointless) with Moiraine, she just sees that he can't do it without Moiraine. And Moiraine being dead, as far as Min knows anyway, invalidates only the vision about Moiraine and Thom (again, from Min's perspective). One vision was a contingent one, the other a certainty. She has both.