While I agree that the whole thing was set up by Moridin, it's in my view simply too contrived to believe that Graendal somehow escaped and e.g. Moghedien was killed. As others said, Moridin actually doesn't care about Graendal. He just used her as a tool to make Rand even harder. One also has to remember that Graendal was Moridin's last serious rival (except for Demandred of course). All other Forsaken had already lost the DO's favor more or less. Moridin certainly knew that Graendal would still plot to kill him, but thus used Rand against her to harden Rand but also get rid of one rival.