If she comes before Congress again before she says a word I would tell her if she makes a speech or opening statement she has waived her right to plead the fifth.
I've wondered about this. The 5th amendment says no witness can be compelled to testify against himself in court. It doesn't say, "Unless he first starts doing it and then stops and say he doesn't want to any more, then he CAN be compelled to keep talking".
Sounds to me like Lerner can give all the opening speeches she wants, and then clam up and not say a further word, and she is protected for doing so by the 5th.
Any other interpretation of the 5th, as written, seems a lot less likely to me.
She's unquestionably a scumbag who knows where the bodies are buried. But even guilty scumbags are protected by the 5th, like it or not. And creative "interpretations" to change that, are illegal.