Or, yes, it might be referring to the battle between Cora and Regina, but in the present Storybrooke? The ‘mental’ battle that Cora would eventually fail, trying to convince her daughter onto her side? It could be a symbolic death, the Evil Queen – “the other woman” inside Regina – could be gone as she wants to redeem herself?
It would tie nicely if, at the same time, we would have some queen dying in FTL flashbacks?