People solo the East Face all the time. It lends itself to soloing, and the zigzag route makes leading it a real pain in the butt. It's very easy to stare at the fresh air traverse from 30 feet away and not see it. It's possible to stare at it from 10 feet away and not recognize it. It's even possible to look right at it from five feet away and think that attempting it will result in certain death. It really isn't that hard, but it looks tough, and as I said, it's easy to miss. My guess is that she did the East Face on purpose, and stopped when she couldn't find the fresh air traverse or some other key part of the route.
