What I believe is probably irrelevant. What I know, however, is not.
Nancy Pelosi grew up in a politicl household - her father was Mayor of Baltimore and a big time player in the Democratic machine politics of Maryland. She has continued the machine ethic of divide and conquer in her own political life. This ethic rests on the assumption that everyone has a political agenda and that all groups have political agendas as well. When an individual or group presents a position that is inconvenient to the machine, the machine works to undermine the group rather than the position.
The Central Intelligence Agency shares many characteristics with the U.S. military. Some individuals have a political agenda, but the larger organization does not and cannot. The larger organization must always deal in facts. When the organization must interpret these facts, it has no choice but to let the chips fall where they may. Sometimes the larger organizationn gets the conclusion wrong, but that is far from intentional deception. Sometimes an individual within the institution goes off the deep end - e.g., Lieutenant Colonel Oliver North - but the larger institution eventually corrects the individual and itelf. Speaker Pelosi's apparent belief that the CIA is just another special interest group with its own domestic political agenda is at best misinformed, just as Vice President Biden's apparent identical belief about the U.S. military.
Throughout history, any country with a politicized military wound up under military rule, quicker rather than slower. Any country. No exceptions. Ever. And, throughout history, any country with a politicized intelligence organization wound up in terror and tyrrany. Any country. No exceptions. Ever. For a view of what terror and tyrrany involve, see Zimbabwe. For a view of what military rule involes, see Myanmar. Anyone who states we are under either military rule or controlled by a politicized intelligence organization is a fool.
Members of the CIA and of the military generally view lying to Congress and its members on substantive issues as a form of treason. Congress has oversight authority under the Constitution which CIA and military members are sworn to uphold. The lie violates that oath.
Representative Pelosi states that, when briefed several years ago, she was told that waterboarding could be used but there was no statement that it had been used. Then, and every moment since then, she has had the authority to demand an answer to the logical question "Have you used waterboarding?" If she failed to ask that question then her level of intellectual curiosity is insufficient to her position. If she asked the question and received a lie in response, then the liar and all who facilitated the lie should be charged and tried.
Representative Pelosi has led a charmed life to this point. She has been able to attack any individual or group whose positions are inconvenient to her, with complete impunity. When she accused the CIA and its employees of lying - treason, really - she crossed the line from impunity into needing to substantiate her accusation.
What I believe is not relevant. What I know is relevant: Speaker Pelosi must either substantiate her accusation or resign.