Why would Becky be tarred and feathered for brewing tea?
Becky says she cannot brew tea because the rebels would tar and feather her for doing so. Remember that leading up to the American Revolution, taxes and tariffs were a huge deal to the colonists, who felt that the British should not be able to increase taxes on them, especially as the British seemed to be doing it as a way to punish and suppress the colonists. Colonists fought back by covering tax collectors in tar and dumping feathers on them, a form of terrorism that stopped all tariffs on imports except for those on tea by 1770.
Tea then became a big point of contention between the Tories (who sided with Britain) and the revolutionary colonists (Remember the Boston Tea Party?) Though Boston rebel leaders decided to stop tarring and feathering, viewing it as a violent action that would make the American cause look bad, many other towns and cities were happy to use it against Tories who seemed to act against the American cause. Therefore Becky, who is the servant of a Tory family, is right to fear repercussions for doing such an anti-American act as brewing a cup of tea.