I don't know much about the series but I have read about Cersei's prophecy and how she's prophecized to die. And it just seems to me that Tyrion is a huge
red herring in that regard. Jaime, albeit only by a few minutes, is her "little brother." I think her downfall will be at his hands while she's either obsessed with Tyrion or lets her guard down after she's dealt with him.
No idea if any of that's gone down already though. Just something that leapt out at me after I read that tidbit.