Ironically in an opposite twist- the episode when radioactive vegetables wash ashore, Mrs. Howell eats the mutated beets which gives her an insane boost of energy. This enables her to perform tasks never done before by her, such as cleaning the huts as well as sweeping the sand in the lagoon.
But in reality, her laziness was her weakness. The fact that she didn't do anything at all was another reason why they never left the island.