i don't recall marika telling me anything directly in the DLC - the most explicit missives i got about stopping miquella came from saint trina and ansbach, neither of which are really any authority on the goodness of miquella's action. (nor is marika, for that matter.)

if anything, i think the base game told you that marika was "guiding" you (indirectly) - she wants someone to free (kill) her, and has set a bunch of things in motion to try to achieve that (e.g. recalling the tarnished to the lands between, making hewg smith a weapon capable of killing her, etc.)