Daenerys’s world is crashing down. Her claim to the throne is in jeopardy, the man she loves is revealed as her nephew, two of her dragons are dead and two of her most trusted and beloved advisors were killed. This isn’t how she imagined things will go along.
There is another fan theory that could be put into play here that really pushes her over the edge: Tyrion being a Targaryen bastard.
There are hints that the Mad King loved Joanna Lannister, Tywin’s wife. When he and Tyrion sit and talk, he admits to believing Tyrion wasn’t his son because he was a dwarf.
With all the potential genetic problems in Targaryens, it could be possible that Tyrion’s Dwarfism came from the Targaryen genes. In the books, he also has platinum hair like Daenerys.
Bran could find this out when casually talking about Tyrion, and then have a vision of Joanna and Aerys.
If Daenerys will find out that even Tyrion has a claim to the throne (as the king’s eldest, albeit bastard son) she will lose it.
At least that’s what I think :)