Place the end of a ruler at the outer nose and put on the corner of the eye, this is where the brow should end. On the model above, she's right on target. Usually, it's only a slight bit if women are outside this last line.
Eyebrow Shaping Tips:
Most of the time over-plucking has resulted in brows not meeting this end point. If that's the case for you, use a brow pencil like Billion Dollar Brows Universal Brow Pencil (buy direct) until it grows out.