The DDA should not be interviewing the victim or witnesses without a third party present (usu the investigating officer).
Anything you say may be discoverable, and it would be an ethical violation if the DDA failed to share that info, and more important, the DDA may become a witness and will be unable to prosecute the case.
Vics and wits should contact the investigating officer if they have additional information or questions about the case (that person is already a witness, and the I/O is responsible for all info/police reports and supplements that are distributed to the DDA, the Court and Defense Counsel).
The DDA is right in not speaking with you, alone. Contact the I/O.