All the examples of whispering Vairelome posted happen after White Night. After Lash has sacrificed herself. After Lasciel's coin was dug up from its place in Harry's basement. Lasciel found out what had happened either at the moment the circle was broken (since Lash is still there she'd have had a link, albeit a weak one) or after she was recovered by Nicodemus (if she was).
But we do not know if Nick recovered Lasciel's coin, so it is all guess work.
JB is referring to the proverb, "Hell hath no fury like a woman scorned." The clear implication is that Lasciel has discovered that her shadow has failed in its mission--to get Harry to claim Lasciel's coin--and is furious at Harry's rejection of her. IF she is aware that her shadow not only failed, but also switched teams and is not "dead," then Mira is right in that Lasciel would be furious at Lash as well as Harry. (There's a chance that Lasciel was told that her shadow had been somehow destroyed, and has not yet found out otherwise. Certainly, once she discovers the truth about Lash, Lash will be right at the top of Lasciel's hit list.)
Exactly, added to that, one of the shadow's fears until she became Lash was death. She openly admitted, Harry dies she dies as well, part of trying to get Harry to take up the coin in White Night was for her own survival. And yes, Lasciel would maybe want to wipe out Lash even more than Harry. Because Lash was part of her, and she betrayed her by taking up Harry's interest over hers. Also, Lasciel might know if Lash wasn't completely dead, even if Bob thought she was. We do have that quiet whisper in White Night that says that Lash might have survived.
I don't see why Lasciel would want to destroy Harry in the first place. She's the Web Weaver, the Deceiver, she's been around since the dawn of time. She isn't human, in any sense of the word. All that Harry has done so far is proven himself to be more powerful than any other host that she has ever dealt with. Keep in mind the sense of scope we're talking about here: Since the dawn of time, Harry is the only one to have not taken up the coin already.
But she is totally pissed, her own shadow betrayed her, her own shadow was changed by Harry, by her love for him. Lasciel doesn't want any part of Harry any longer unless it would be to twist the knife in his gut and cause him more pain.. However she cannot do that unless he agrees to take up the coin. If that was her aim, the time to seduce him with that was when he was flat on his back with no hope of saving little Maggie. However she didn't go for that, she went for, "and it is all your fault.." Best revenge Harry crippled with the knowledge he daughter died and he was helpless to save her.. Or she understood the spell that the Red King was going for, and figured Harry would die anyway, with the agony that he couldn't save his little girl on his mind. She underestimated Harry, he did figure a way, I do not think she figured on Uriel taking counter measures when she whispered those words.
