If Meera Reed is killed by a card effect (say Flame-Kissed or VB) and I use Call of the Three-Eyed Crow to put her back into play she goes Moribund: Dead Pile to Moribund: Play, but she left play briefly, can I trigger her effect to put her back into Shadows, or does the window not allow for this since she's still in a Moribund state? I really want to like Call of the Three-Eyed Crow...

Actually I'm pretty sure she's still Moribund: Play and cannot go back into Shadows.

Correct. While she is "Moribund:Return to Play," you cannot use her effect to make her "Moribund:Shadows."