She not only begrudged them every mouthful they ate but she was on tenterhooks lest they discover somehow that Pork had slaughtered one of the shoats the day before.
Joel says that Susanne is on tenterhooks because she is waiting around; she is waiting for the results of her exam to arrive and she's psyching herself out.
However, combined with the much bloodier war in Gaza and its fallout in places like Egypt, Jordan and Lebanon, the missile skirmish leaves the region on tenterhooks—and its commercial ambitions in a state of uncertainty.