  When it then goes on to show Avi's future, I think that Avi is correct that she has accidentally broken the ter'angreal somehow. I think her talent is the likeliest cause, but it might also be related to her already having some knowledge of her ancestors' history.  This is where I get a bit more speculative: I propose that in extracting that data from the genetic memory of the previous users, it has had to store that information somehow. Then, when Avi breaks the ter'angreal, it malfunctions, and extrapolates a likely future based upon the information it presently has, plus the data Aviendha contributes, and shows her the future by showing her the lives of likely descendants. Because it's not designed for this, it then breaks.  Hence, the future it shows is not taken from a Mirror World, but rather from the the data of the previous occupants. Thus, the future is completely made up, but also incredibly likely - potentially not taking into account the alteration made to it by its own act of showing the future to Aviendha.  I'm opposed to the mirror world idea, because as far as we know, it doesn't function by using TAR to create virtual realities like the Testatron ter'angreal the AS use or appear to tap into mirror worlds in any way during the course of its normal function. I think it's broken because Avi senses nothing from it, and there may be evidence she can read even a ter'angreal which she can't use. And I put those two ideas together to reject the notion that it might have some unused mirror world scanning function lying in wait for Aviendha in a similar way to how Callandor was warded against any except Rand, especially since there is no mention of Aviendha in the Karaethon Cycle (or any prophecy more than a few years old) that I'm aware of.  