Hmm. At one point Jack muses that Wanda's mind had been badly broken and put back together poorly. We assumed this happened in Book 1 when Jillian broke the spell on her. But what if Wanda's mind got smashed earlier than that?
Or it could have just happened twice. There's no reason to assume that (given her behavior before and after) the mind control backlash didn't break her mind. Which, of course, means that she's cracked more deeply than we ever figured.