There is foreshadowing for #Daenerys going mad, but slaughtering common people is completely out of character
Whenever she does show cruelty or hints of madness, it’s towards people in power who she believes to be oppressing the common folk (slave masters of Astapor and Mereen being an excellent example). She believes she is a savior, not realizing how fucked up she becomes
In S1 she tries to protect the Lhazareen even though that was how Dothraki conquered normally. She locked two of her dragons in a cell because Drogon burnt a child
And in the books, we get plenty of foreshadowing where she just wants to kill every highborn in order to improve the conditions of freedmen. One of her gripes is that she can’t because she’s be a butcher but that’s her first instinct
Personally I believe we’ll see something similar in the show. She gets the Iron Throne, but her policies are resisted by nobles and she proceeds to burn them
That’s consistent with the madness of her father, and “good king” Aegon the Unlikely also thought that with dragons it would be much easier for him to pass these kinds of policies. Targaryen madness has never been genocide in a murderous rage
But because the show is so rushed, and there’s really no more smaller noblemen she could burn now that the show has reduced the scope of the world to three houses, D&D needed another way to show her sliding into madness
Which leads to her burning a whole city down before flying o the Red Keep in a way that is completely antithetical to what her character is and turns her into one of the most bloodthirsty people in Westeros’s history #GameofThrones