hi, just new here and thought I would add my two cents on a question I've been puzzling over since the end of black ice...
I don't think she knows about Heritas Cant - my impression was that Angus never told his daughters anything that might harm them - knowledge of the name and whereabouts of a powerful magic user and member of the phage falls into this category, I think, so that rules out Cant.
Chasing the Maiden? Possibly - but I think Heavymetal makes an interesting point. We know how protective Crouch was of her hands - having them set on fire might have distrated her sufficiently for Cassie to get a chance to kill her. ALthough why, then would she bury the assassin? (possibly, being a smart young woman, she knew that if there were the right amount of graves everyone would assume she was also dead, ruling out future assassins hunting her).
No, I think that Cassie has gone looking for the only family she has left - her father and the Sevrances. Last she knew Angus and Raif were heading north, so I wouldn't be suprised to see her showing up at Blackhail asking for news of Angus, Raif or any Sevrance, for that matter.
Another thought - since she would be heading North, asking about Raif and possibly badly burned from the fire, what does anyone think of the possibility os her showing up at the Rift one of these days?