Re: Theresa Evil?!
I vote evil, or at least evil-ish (and am currently writing a fanfic to that effect, since you mention it. Help. I'm fanficcing Fable. xD). I agree with the OP that it's possible, even likely, that she arranged things so that Hammer had 'a reason to fight', and it's also highly suspicious that she effectively set the whole plot of Fable II in motion by encouraging the young Sparrow and Rose to buy the music box.
As for her motives... perhaps she wants to bring back her brother and/or Jack; perhaps she truly believes that Albion would be better under her control, and intends to use the Spire to that effect. I don't think that her potential belief that she should be In Charge conflicts with wanting Lucien gone (even though he wanted essentially the same thing), as if that is her goal, like all good megalomaniacs, she probably thinks She'd Do It Best Anyway.
And as to her long life, I'm going on hazy memories here, but doesn't the blood of Archon (sp?) have the potential to make one immortal or close to it?
Right, Falcon out before I start to ramble.