If that’s the case, then Cersei’s position in King’s Landing (possibly with the backing of a certain Greyjoy) is much stronger than expected.
One scene in Season 7 will evidently feature Cersei Lannister facing off against Ellaria Sand of Dorne.
If she somehow manages to outmaneuver an enemy comprised of Olenna, Oberyn Tyrell’s family, Varys, and perhaps even Daenerys, Cersei could remain a strong player in the game.
Given that Ellaria has been clapped in irons, Cersei looks quite at her ease, and Ser Robert Strong is on hand, I’d say that Ellaria’s plot with Olenna Tyrell probably didn’t go well for them.