Complex sentence: Unable to resist his proximity, Buffy shivers and leans back, then--in this relative safety, with nowhere else to immediately be--begins to cry in reaction to all the stressful events of the past two days.
Split into simpler sentences: Unable to resist his proximity, Buffy shivers and leans back. Then, in this relative safety, with nowhere else immediately to be, the Slayer begins to cry in reaction to all the stressful events of the past two days.