Hey, I said she was SUICIDAL, not SANE. I mean, really... what was her motivation for poking around in a past, knowing (and she would have to know) that it would stir up a chain of events that she'd have access to memories of... and would eventually lead to her demise.
Also, she never *really* used the time-compression as it was implied, not fully at least. Otherwise, how would all the beings still alive in her era exist? Monsters and those SeeDs alike? Either compression is a localized phenomena, a lot of beings actually can handle it, or it was never truly completed. And it'd make for some very GOOD motivation to manipulate the heroes into killing her... something that, regardless, she'd have memories of through Rinoa and Edea's mind. One kills her, the other absorbs her powers- dunno about you, but THAT's something that would stick out in my mind. Scale of 1 to 10, those two events get an 11 and 12, perspectively.