Grand Juries are very "secretive" but also have very lax rules as the normal evidential rules do not apply. To me your question seems to mean the DA told the complaining witness that one of the suspects or maybe the suspect of the Grand Jury is not appearing today or maybe just won't be present while she is testifying. If that's the case there's nothing wrong with giving a witness some details or maybe calming them down letting them know a suspect or the suspect isn't going to be there.
You said, in your comment to another answerer "DA called a third party outside the grand jury room and told them a target of the grand jury would not be appearing ."
The 3rd party could have been:
1. Her boss
2. An attorney who needed to serve the target in person
3. The witness' attorney who needed to be there to help
4 Her husband to let him know she will not be home late -- because the lengthy testimony of the target would not be occurring...
5. Many more possibilities.
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