ORIN KERR: Can A Congressional Witness Deny Guilt and Then Plead the Fifth? “I don’t think the answer is clear, as there are no cases quite like it. The general rule is that a witness can’t testify about her version of the facts and then invoke the Fifth Amendment when facing cross examination.”

Alan Dershowitz says she waived.

Also: WaPo: Did Lois Lerner waive her right to invoke the Fifth Amendment?