She knew from the beginning. According to a CIA document compiled by the Director of National Intelligence summarizing briefings to Congress on the use of enhanced interrogation techniques on terrorist detainees, House Speaker Nancy Pelosi (D-Ca) knew from the very beginning that those techniques - including waterboarding - were being used on September 4, 2002.
According to the memo the very first briefing listed is 9/4/02 with then Rep. Porter Goss & Pelosi. The summary of the briefing says:
“Briefing on EITs including use of EITs on Abu Zubaydah, background on authorities, and a description of the particular EITs that had been employed.”
This directly contradicts Pelosi’s story, that “we were not told that waterboarding or any of these other enhanced interrogation methods were used.”
As HUMAN EVENTS reported earlier, Pelosi - by objecting to the use of the enhanced interrogation techniques - could have stopped them but didn't.
Pelosi's misstatements were apparently intended to divert attention from her and other Democrats in Congress who knew of all the enhanced interrogation methods - in detail - apparently as soon as they were being used. 
