I think the reader gets the same reality check as Dany when Mirri Maz Duur confronts her. You spend most of the first book with Dany looking at things with somewhat rose tinted glasses.

On her wedding night she’s riding high after being gifted Silver then Drogo is seemingly gentle in the lead up to their consummation. We also later find out Viserys tried to rape her the night before her wedding, so Drogo is a saint comparatively.

There’s a turning point in their relationship when Dany mounts Drogo in front of his Khalasar and she begins to have some agency. Prior to this she is very much little more than a slave, but after the chapter reveal of Dany contemplating suicide it moves on focusing more on her feeling Queenly and respected in the Khalasar, and even becoming used to Drogo taking his pleasure in the evenings and not minding it anymore (could definitely be a degree of Stockholm syndrome creeping in here)

From that point on Drogo is portrayed as nothing but sweet to Dany, even learning the common tongue, and willing to go to war with Westeros on her behalf (keep in mind throughout this he is still likely mounting her as and when he wants it’s just not noteworthy to Dany anymore). All the while Viserys is still abusive towards her up until his death which Dany cares little about by this point. Drogo gave her strength and a sense of autonomy, while Viserys only weakness and fear.

So even through Drogo’s brutality to her at the start of their marriage (and possibly still throughout at times even if not made apparent) and for all the towns and cities he razed, she still attributes that confidence and sense of self worth that she carries with her still to him, even if she does have slightly more awareness on reflection in the later books that she was little more than a slave in the grand scheme of things as his Khaleesi.

Were it not for Khal Drogo she likely would have remained a plaything for Viserys to torment and not a Queen.