Angela knows good and well that Ghost did not kill Greg. She is acting like she did not know, but she has been with Jamie (Ghost) long enough to know that he would not kill a cop. Now, what she also knows is that he would never in a million years plant a gun inside the club. Prior to being confronted by Tasha, it was revealed that the death penalty would be issued to Ghost if he is found guilty of murdering the cop. While she is playing tough on the outside, she still loves Ghost and more importantly, she knows that Jamie is a father of three children.
In the second episode of Season 4, we saw Ghost at his most vulnerable state. His children came to visit him (prior to him finding out about the death penalty) and you could see him break down. He is in a position where he cannot do anything to protect his family. Now early in the episode, we saw Angela and Jamie both get questioned simultaneously about their relationship. As Angela is reliving her relationship with him, you can start to see her love for Ghost in her eyes. But it got real when they discussed that death penalty. My prediction is that she will tell them to review the footage from the club surveillance cameras and that is where they will see the gun planted by the real killer. Another thing? Have they not realized that the murder weapon is issued by the FBI?