My take on jasnah ( mostly from the WoR prologue ) was that she is a control freak. I am still inclined to think that the final break would have been galivar's death. This cannot the be whole of it, since ivory found her 'interesting' before then, but the end of that section is heartbreaking to read.. In spite of her efforts to protect her family, Her father is dead, she watched it happen, nothing about it makes sense...and she cannot find any answers....
I also wonder if she really is as proficient in elsecalling as people assume. Sure she's (probably) bonded ivory for years, but until the end of wor, we never see her manifest a shardblade or make use of transportation. Navani indicates that she avoided assasination attempts and simply 'reappeared somewhere else', but that could have been instinctive. prior to the end of wor, i dont think shes said more than two ideals. i think one of the things shes searching desperately for is WHAT she is supposed to say to progress, but the heirocracy removed any written record of the ideals. I think she found them in shadesmar.