Joy.
Another Red Crossing/Exalted March on the Dales discussion. Those are always fun, enlightening, and filled with people rationally and logically examining all available evidence without bias. 
Here's my contribution:
Some people a few pages back suggested that if Val Royeaux had been sacked that Mother Giselle would have mentioned it. However, Mother Giselle's purpose in that dialogue is explaining why the Divine declared an Exalted March. It wasn't an in-depth discussion on the war overall. Just a primer on why that one specific decision had been made. Orlais was at war with the elves, they had already sacked Montsimmard and were readying to attack Val Royeaux. She doesn't give any more details beyond that, because no more details are required. That doesn't mean Val Royeaux was never sacked, just that it happened after the Exalted March had officially started. The war lasted ten years. The elves had numerous victories in that timespan. She doesn't discuss those either.
Onward to Red Crossing! 
We've had multiple codex entries about the events of Red Crossing. One contemporary. The rest not.
The ones that are not all suggest that Red Crossing was completely wiped out.
Now, the one that actually is contemporary.... doesn't actually say one way or the other.
This isn't surprising because the codex entry isn't called, "Everything that ever happened at Red Crossing until the Fall of the Dales" it's called "The Death of Elandrin" it is about... surprise, surprise, the death of Elandrin.
AKA, the part of the narrative of Red Crossing that the Emerald Knights felt guilty enough about to dedicate a large chunk of their tomb in remembrance In secret of course, so they wouldn't have to admit their guilt out loud where other people might hear them say they were wrong about something.
So let me take a close look at the actual text of that codex entry and figure out what it all means.
Elandrin, our brother.
Falon'Din guide you. Maker guide you.
Let here the truth be kept, lest you be remembered a traitor, or our sorrow seem a passing woe.
Though you swore to serve our people, there were those questioning your heart.
Translation: Oops. Our bad.
(1)Too often had we fought with humans along our borders until the beginning was lost to memory. (2)Rumors of an abduction stirred. (3)As always, their Chantry was swift to spread lies. (4) In haste and anger, they killed Siona's sister for wandering too near the hunters' path. You carried her body back to us, you mourned with us—yet your heart was distracted. Siona begged for vengeance and you turned away.
The first line likely refers to the various conflicts with missionaries and Templars mentioned in the Dalish accounts. And the conflicts the Chantry claims were between traders, diplomats and other innocent and unassuming folk with the Emerald Knights. This implies that even the Emerald Knight writing this doesn't necessarily know which is true.
The second and third lines likely refer to things like the (possible) anti-elven propaganda mentioned in the Codex entry on the Dales.
"Dark rumors spread in the lands that bordered the Dales, whispers of humans captured and sacrificed to elven gods."
And in the fourth line, 'they' in this case is most likely referring to humans, and not the Chantry as in the previous line the Chantry is also called "theirs" So it was humans who killed Siona's sister. Not the Chantry. Although they are believed to have been motivated by Chantry lies.
It is not clear if this happens in human territory or elven.
It is not clear if these humans are from Red Crossing.
It is not entirely clear if Elandrin was a witness, or simply recovered her body later.
What is clear is that Siona wants blood. Elandrin wants none of it.
More and more you vanished without word or explanation. When whispers rose that you would swear yourself to their Maker, we feared what would come.
More and more he vanished. This is an indicator that some measure of time has past between the sister's death and the attack on Red Crossing. It could be a month. Could be a year. But it's unlikely to have been a matter or days or even weeks.
Siona sought to save you, to bring you back to us. She had lost a sister, must she also lose a brother? Beneath the trees she saw you with a woman, the one who turned you from us. The woman gestured toward the village. You and she turned to gaze upon the Chantry's walls.
Siona returned. She told us how humans were turning you against us. How their lies must have filled you. As a loyal servant to the Maker's cause, you would betray our secrets. When we went to ask if there was truth in this, you were already gone.
Siona doesn't have any specific knowledge of what Elandrin is up to. She just assumes that if he's able to have a peaceful conversation with a human woman and can look at the Village's Chantry without setting it on fire with the force of his glare, he must be a traitor who will aid in the destruction of the people he's sworn to protect. This is of course, precisely the rational sort of thought process I expect from the Elves at this point.
She obviously blames Adalene for it.
So we sought to stop you. With haste, Siona led her people to the village. There we would challenge you. There we would bring you back to us... or to justice.
"her people" is very nonspecific. It could mean there were a five, it could mean there were twenty. or a hundred. They are going to go directly into the village and take Elandrin out by force if necessary. They might not intend to be seen as an invading force. But yeah, they are a bunch of Emerald Knights, invading Red Crossing.
In the dim of a moonless night, she saw Siona through the trees. She raced toward Siona, a cry on her lips and something in her hand. Siona's arrow flew. So the woman fell, the name "Elandrin" dying on her lips, daisies slipping from her grasp.
Adalene doesn't run screaming like a banshee as someone earlier implied. She sees an elven figure in the woods in dim lighting, expecting that it is the lover she intended to meet, she begins to run toward it and is shot dead before she can even finish calling his name.
Siona has been depicted so far as a vengeful human-hater, a woman who would assume that her sworn brother is a traitor out to get them based solely on his ability to have nonviolent interactions with a human woman. So I wouldn't rush to defend this as an unfortunate accident.
The men of the village suspected the girl's flight, and heard the scream. They fell upon the elves, but were no match.
The men of the village is also very nonspecific. It could mean a dozen. It could mean thirty. All were killed by the Emerald Knights. Unsurprising. Considering the Emerald Knights were prepared for armed conflict and the men of the village were likely armed only with makeshift weapons if they had any weapons at all. The codex does not mention any elven casualties at all.
Siona's haste surpassed your own. You knelt beneath the trees, blood-soaked petals clinging to your clothes from a final embrace. When more humans came, you would not be moved—and they would not listen. Their arrows found your heart and you fell beside her.
My reading, Elandrin arrived shortly after Siona killed his lover and the first group of villagers. He is understandably distraught, as any young elf would be after realizing his friends and family murdered his lover. So when more villagers came he refused to return with the other Emerald Knights, and the humans killed him because they assumed he was responsible for the carnage.
And here is the most important part of the codex entry:
We found your body in the river where they cast you aside. She was taken by her own. It was not the end, but your part is past.
It was not the end, but your part is past.
It was not the end.
The Death of Elandrin is not the end of the events of Red Crossing. Given that even sources that are biased toward the elves indicate Red Crossing was wiped out, I see no reason why those accounts should be discarded. It just means that Red Crossing wasn't properly massacred until after the events described here.
Rest now as our honored brother once more. A wreath of daisies at your brow, the letter she carried in your hand. Whoever guides you, whoever guides her, may your souls meet once more in the beyond.
Faded blood stains the letter:
Adalene,
What care have I for gods I have never seen, for a Maker I do not know? Let others distract themselves with such lofty concerns. I know only this life, I have seen only this world, and I care only for you.
Perhaps your priestess distrusts the sincerity of "uncivilized" elves. If she must hear me say I will follow the Maker, so be it. Your god intercedes as much as ours. My life will not change.
I will return in two weeks' time. My heart longs for you 'till then, and will remain with you forever after.
Elandrin
There is a lesson to be learned from all of this: Never romance an elf. Or your village will probably be slaughtered. 