She is simply a witness. She doesn’t need to have any other information about the case presented to her and, really, she shouldn’t have because that might taint her testimony. Her obligation is to appear and answer the questions put to her truthfully. That’s all she has to do. Now, if the answers to any of the questions might implicate her in criminal activity then she might need to invoke her right to refuse to answer under the fifth amendment. If she has any concern that this might occur she should consult a criminal defense attorney for advice before showing up to testify so she knows what to do.

