So much is being assumed about what happened between the witch of the wilds (Flemeth, most likely, but never named) and Maric in that meeting. But the truth is, nothing about it except the betrayals by Loghain are mentioned specifically (that I know if.) I haven't been able to read the Calling because it's not out in ebook format yet.
So it's all speculation. However, if one remembers the scene, where Flemeth tosses the apple core out, and then it vanishes, and Maric (it is Maric's point of view, right?) believes he sees a pair of eyes there.... maybe those of a snake?
Morrigan has a habit of watching in animal form. We know Flemeth is already there in human form... We know what the toolset says Morrigan APPEARS to be..30. But Flemeth APPEARS to be an old woman. But she doesn't look centuries old. And who guessed, before the first fight, that she'd turn into what she turns into? What is Flemeth's true form? Age? Morrigan's? We don't know her real age. She might be 75. She only appears to be 30ish. She might have been there that night with maric, watching from the sidelines.
so much conjecture, but so little fact. I highly doubt that there's anything to do with sister babies or anything like that. It's something else. What else, I cannot say. But that other set of eyes strongly suggests Morrigan is older than she appears, just as Flemeth is far older than she appears, and that appearances, int he case of these two witches, are nothing, if not deceiving. Who knows how much either of them ever say is truth?
And without knowing the truth of the substance or form, how can even guess at intentions?
I say, some mysteries are just more fun as mysteries.