One can only be taken advantage of with permission - it's been given and taken up on. 3 months turning into almost a year plus a b/f means she's now full fledged family member. Family members are expected to help out, even extended ones. Give her a list of chores she's expected to do, and if not happening, start charging hotel-rate rent - if the niece won't pay send it to the aunt. If the aunt won't pay give one month's notice to find a new place. Life is simple, it's people who make it complicated.