I would bring it up once, in a calm, civil tone. Let her know that she decided to leave and she no longer has free rain of entering the house and removing items. No arguing, no yelling. Let her vent (if she does) afterward and validate.
While I do see NYs point, I think that some tough love and letting the other person deal with the consquences of their actions can also be used. Plus, to me, it shows dettachment, showing them you are moving on and need your privacy and own space.
