I actually liked the episode and felt it very believable (in the context). I found it was quite plausible that Beth's character would snap; a teenager who over the last few years had seen her entire family taken from her in a variety of awful ways. She showed signs of depression and PTSD and had in her mind associated Dawn with all that was wrong with this world (much like the Governor) and the antithesis to her father's role model of compassion. A sloppy attempt of premeditated murder was quite realistic as she has never been portrayed as the grizzled proved killer. And to be honest her death and the tragedy of it brought out the compassion in Rick to offer help to those who wanted to leave the hospital and away from this environment that had led Beth to do what she did. A stark contrast to the Rick that we have seen that has lost all mercy and a reminder of how Hershel had tried to bring Rick's humanity back before he died.
