I liked this episode for the basis of the what was offered - you do X and ONLY X and see where you go from there.  It seemed like she was actually going to do X and ONLY X but thought that there was more to it than that.  Perhaps she should have asked a few more questions and then she would've done the right thing as it was obvious that it had bothered her for some time.  I did like the twist ending as well, but I wonder how taking her out of the "present" (as she just replaced herself doing the same thing in the past) and putting her in the far past affects the future (or even the "present").  If you watch Doctor Who you know that "small people" can make a big difference.  Of course, both are fiction so take that as you will.