Reviewing the Lostpedia page on Rousseau: After killing her teammates, she goes to the Radio Tower and changes the signal. Three days after that she gives birth. A week after that the black smoke column appeared and the Others took Alex.
If I recall tonight's ep correctly wasn't there a black column on the day she killed Robert? If so is this a continuity error, or Rousseau lying/misremembering her past?
Also, Rousseau claimed the Others infected her teammates with the sickness in S1. And we didn't see her hearing the Whispers for the first time, either.