Immunity for more lies? Why would anyone believe anything she says? Hold her in contempt and put her in jail.
Well.. if she lies on the stand, she'll face a much clearer charge of perjury.
Maybe she’ll be able to provide more hard and direct incriminating information such as emails and telephone communications (if they haven’t been destroyed yet of course). Her testimony may not be necessary; just her knowledge of where and what things are hidden.