Only thing Cersei is going to do is what she's always done, which is be a gigantic moron and fuck up the carefully laid plans and alliances smarter people than her worked to build. The prophecy of Cersei dying at the hands of her own brother is probably going to end up referring to Jaime, not Tyrion as she always believed. Jaime going to be an unsung hero yet again by killing another insane, torture/fire loving absolute ruler. An even bigger sacrifice than just his honour this time, since it's Cersei, the only person he's ever really loved.