quote: "I'm sorry, you lost me on this. Could you explain?"
Well I didn't get to watch too much of it, but several points would be(not actual quotes)"the president was never briefed", and "the FBI was notified and corrective action was put in place"......basically everything she hastily wanted to "correct" after so much evidence surfaced that refuted her first testimony.
Refusing to testify was a kicker. Oh could you pretty-please?
Perhaps lying was too strong a word. Evasive, elusive, interfering with the investigation probably would be more appropriate. The commitee seemed a waste of time and money because both the parties seem motivated only by partisan actions nowadays.

You should try to read the transcript when you have time. The things she was correcting were Clarke's testimony, not her prior testimony. She did not refuse to testify...she was kept from doing so in public for the same reason as Clinton, Gore, Cheney, and Bush...pecedent per presidential privilege and separation of powers.