She Dies to Fulfill a Prophecy
If there's one thing Daenerys and Jon have in common (aside from genetics) it's prophecies. The two are involved in so many, it's hard to keep them all straight. But one thing is obvious: one of them is meant to die in some horrific way. The most popular theory around is that Jon is Azor Ahai, which is cool but means that Daenerys is the stand-in for Azor Ahai's wife, Nissa Nissa — which ends in her death. Yikes.