Game Of Thrones Season 7 Implications: What "Stormborn" Really Means
9. Dany Sees Varys For What He Really Is
So far, Dany seemed to be hoovering up allies to her cause with absolutely no security checks, simply because they were the enemies of the Lannisters. She's previously co-opted Tyrion, Varys, the Sands, the Greyjoys and Olenna Tyrell, without so much as a question over their agendas (beyond knowing Cersei has wronged them all in some way).
Now, it seems she's beginning to question a little more, as she picked away at Varys' allegiance, rightly questioning why she should trust him when he's been behind the fall of more than one king (including her father). Though his other allies have seemed to miss the point of how dangerous he is, Dany's exchange with him proved that she has his number and that she knows exactly what to expect from him.
It wasn't exactly the start of friction between the two, but more a reaffirmation that both of them want what is best for the realm and its people (though Dany's motivation for the Iron Throne has always primarily been that it is what is owed to her - as an extension of her brother's agenda). And in challenging Varys, rather than undermining her power, she seemed to grow in his opinion, which is always a good way to protect yourself from the dagger he'll stick in your back.