Ah yes of course, not sure how someone didn't clue into that earlier! Good job guys.
For a 1 cost I imagine it does exactly the same thing as leave no trace but is instead "after an non-unique enemy is destroyed" instead of "after a non-unique location is explored". This makes Keen as Lances far more useful and Rossiel as well.
Really cool hero design and potential to be very powerful in the right deck. Just take note of what enemies and locations you add to the victory display (make sure you remove ones that have the same trait as many other encounter cards in the current quest) and she could quite regularly have both her willpower and defense boost in the same turn. Low starting threat and a nice trait (wish it was noldor though) are also bonuses.