A VERY disturbing theory....(possible spoilers)
So, based off the achievements, we know Sarah's probably going to die or drastically change in some way, Clementine is going to witness a murder and Clementine is also going to get the shit beat out of her. Judging by the picture for the beat down(not in nottingham) achievement(the picture is an eyeball looking at someone), Clementine probably gets 'beat down' by the same person who murdered someone, after witnessing the murder. There is evidence Sarah might die....
One character I believe would have no problem murdering a child is Becca. Maybe Becca murders Sarah(they have completely opposite views and I could see them getting into a fight VERY extremely easily) and Clementine attacks her for it but gets 'beat down'. Or perhaps it's just a very difficult fight to win(like the fight between Lee and Molly, it goes by sooo fast it's hard to react).
Let's say the options here are -
Watch the fight between Sarah and Becca play out or try to stop it.
Be aggressive towards Becca after she kills Sarah, promise not to tell anyone and be a scaredy cat, or sympathize with Becca.
Win the fight or Lose it(just based off how you think you would handle an extremely difficult to win fight, like the one between Molly and Lee but longer).
I would try to stop the fight and probably be aggressive towards Becca. Though I might be inclined to sympathize with her if given a good enough reason. I think I'd probably not be prepared for the fight, lose then rewind and win.