She technically died in Lothering in my first game, I never met her.
She broke in my second game, got her agreement to high and she broke cutting off all her dialog, quest, and ability to care that I defiled the ashes.
Third time she actually functioned and I managed to not hate her.
If they provide an official explanation, or short story, or flash back in future Dragon Age installments explaining what magic or luck allowed her to live, then I'll continue my initial response of "Fair enough, Wynn was dead, My Warden should have died but didn't thanks to Flemmeth, then thanks to her friends, then thanks to Morrigan."
In my game's case it could be as simple as, "Well of course she didn't bloody well wait around and die to the Darkspawn and fire!"
I think I'll choose to believe she waited long enough that my Hawke knew her, maybe helped her escape.
If people are going to be hard on bad writing, be hard where it's due, Leliana's DA1 DLC.
Big narrative "omg that was my journey I'll leave you to decide how it ended... Even though you already explicitly know that I didn't die, and she didn't die, and then I came with you, and then we killed her, and then I explained all this in as much text as it really needed."
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Beyond all that, almost off topic really.
Cameos make the world go round.
I would have liked Dragon Age 2 significantly less if it weren't for Flemmeth, Alistair, Leliana, the Shale rumor in the Hanged Man, Zevran, Anders, Merril etc.
Amazingly enough they all lined up flawlessly with my DA1 game. Awakening and DA1 had more issues with themselves than DA2 did with consistency.