Corey's case may well be that Zimmerman started the fight, or at the very least provoked the fight. See my last post - it all depends on who was chasing who. If Zimmerman started/provoked the fight, then even if Martin had the upper hand, it is very difficult (as a matter of law) for Zimmerman to claim self-defense.
Corey has zero evidence for this, and Zimmerman has a history of successfully mentoring a black youth and working with and alongside blacks. He has no admissible history of violence, aggressiveness or provocation.
Corey cannot testify or give evidence, and her speculation will be clearly identified as such with no evidentiary backing. Zimmerman's testimony (if he chooses) is evidence and is backed by substantial other independent evidence.
If Zimmerman is properly prepared for testimony, Corey is looking to be Nifong's roommate.
The problem for Corey is that there does not seem to be any evidence to support the theory that Zimmerman was "chasing" Martin. Even in the link you gave, the witness states he/she could not see who was chasing whom. (That is the only witness to say there was a chase, also, and the statement came several days after the incident - raises questions of credibility and accuracy.) And there are at least 2 witnesses who state that they saw Martin on top of Zimmerman, beating him. So the only question the defense would have to ask is, if Zimmerman was chasing Martin, how did Martin wind up on top of Zimmerman? That is enough to raise reasonable doubt all by itself.