My take on the ending
FIRST OFF I just finished lily today and signalis is one of the few games that makes me physically feel things like generally it's so beautiful. But my idea of the ending is aria transcends and breaks the loop herself because no matter what elster keeps falling refusing to kill her ( i love promise though) and what we see is essentially the after life of them she dies and takes elster with her ( the grave at the end of lilly) and the live and dance for the rest of their shared afterlife or promise is true but they share an afterlife together