The worry I have is not her current position, it's the possibility that Wall Street may promote her to CEO in the future if they like her enough. We know from WDW1974 that Iger had intended former CFO Jay Rasulo to be his successor at one point, he was grooming him for the job and apparently giving him positive feedback for the BoD. So it's not exactly impossible (or even unlikely) that a CFO could be given a position of greater power.
Don't read anything more into this move than the obvious. This isn't something that requires deep thinking!