If she and her husband were the size that you indicate, I would think the two of them could have comfortably shared 3 seats, and probably should have been required to do so. However, as Allan38103 said, she was there first and you sat next to her. I don't see that either of the two previously seated passengers should be required to move so you, at at high B boarding position, could claim an aisle seat. I'm assuming there were other seats still available to choose from when you sat in the encroached upon aisle seat?