Get rid of Aerie the first chance you get, shes a very useless character. Replace her instead with Viconia, I believe you can find her about to be executed for being a witch in the Royal District. It doesn't even matter if you've rolled a good character, as I had a Lawful Good character and I even romanced Viconia.
I think theirs even a point in the game where you can get her to switch allegiance but that might be in the Throne of Bhall expansion. You need to be in a relationship with her anyways. (ahh how I miss old Bioware where romancing characters actually changed things as opposed to what we get now where its a excuse for an awkward cut scene for nerds to get off on.)