I'm saying she's the spren of roshar, but thats another theory for another thread. In short, my logic is:
Ba-Ado-Mishram has a powerful connection to everything in Roshar, spren or singer. When she was imprisoned, all of Roshar was damaged. You don't see this for the Thrill or the midnight mother when they where put in a rock. Additionally, it's not unreasonable to assume The Planet of Roshar has a spren, which is conspicuously absent in the story right now.