Game Of Thrones Season 7 Implications: What "The Queen's Justice" Really Means
9. ...But She's Becoming The Mad King
Having already tied herself to the Mad King twice already - in her burning of her enemies in the Sept Of Baelor and in her repeated mantra of being surrounded by enemies on all sides - Cersei took another step towards becoming the image of Aerys reborn in her punishment of Ellaria Sand.
By shackling the Sand Snake leader agonisingly out of reach of her daughter, who Cersei had poisoned and promised would die and rot in front of Ellaria until she herself died - Cersei mirrored the Mad King's murder of Brandon and Rickard Stark.
When they came South (separately) to seek vengeance for the perceived abduction of Lyanna Stark, Aerys imprisoned them and murdered them, stringing Rickard up over a fire and tethering Brandon by his neck with a sword just out of reach that he could use to cut down his father. Ultimately Brandon strangled himself trying to save his father and Rickard was cooked in his armour in a harrowing display of evil.
That final image of Ellaria and the doomed Tyene reaching out for one another was that moment reborn (and arguably with worse implications as Ellaria has no hope of the release of death). And sadly for Cersei, that parallel makes it even more likely that she's going to be killed the same way as Aerys - by Jaime, when he realises his duty.
You can read a more developed analysis of Cersei as the new Mad King here.