Yes, Nancy Grace was ethical as prosecutor, because she did not do her job like she does her current job. The job she has now is to get a TV audience. She is not limited to the Rules of Evidence. Many of the ethical obligations that apply to prosecutors do not apply to her.
I do not think that Nancy Grace was very ethical as a prosecuting attorney. I feel that she has too many biases and allows her own personal thinking to direct her line of questions. I think that she would do just about anything to prosecute someone who is being tried.
No, Nancy Grace did not use ethical practices as a prosecutor. Three different times, appellate courts cited her misconduct in prosecuting cases, because she was willing to push the envelope to gain convictions. Her belief that all arrested suspects are guilty continues to show itself when she makes comments on her television show.
Nancy Grace's conduct as a prosecutor are infamous. Her cases have been reversed at every level of the Judicial system. Her conduct has cost innocent people to be convicted, and guilty people to go free because of a mistrial. She may be able to entertain a jury, but a prosecutor should be seeking the truth, not an audience.
Given that Nancy Grace is far from ethical on her television show, I have my doubts she was very ethical as a prosecutor. I believe Nancy Grace is what is wrong with the society when we can have a TV personality declare people guilty even before their trial happens. She should be taken off the air.