A couple of  thoughts, and here’s my take.  The special prosecutor realizes she doesn’t have a case for the Grand Jury to hear;  Not enough evidence.  Backing away from a Grand Jury quickly provides her more time to focus on a making a case with weak evidence and avoids a potentially disasterous quick jury dismissal.  It would be hard to proceed with any charges if the Grand Jury could not indict.
Also, supposedly “DeeDee” has only ‘just now’ talked to federal authorities; presumably so-too the State Attorney.   I’ve a hunch this “girlfriend” is viewed very suspiciously, for obvious reasons,  and will be thoroughly checked before any weight is provided for her information, or potential testimony.   
However, this also looms as troubling for George Zimmerman, because it shows a propensity of the prosecutor to bring charges despite the flawed or non-existent evidence.  If she (Angela Corey) had a case you can be certain the Grand Jury would be seated to hear it.  However, removal of the GJ from the process just speaks to an agenda of persuing Zimmerman regardless of factual evidence.  
ORLANDO, Fla. — A grand jury will not look into the Trayvon Martin case, a special prosecutor said Monday, leaving the decision of whether to charge the teen’s shooter in her hands alone and eliminating the possibility of a first-degree murder charge.
That prosecutor, Angela Corey, said her decision had no bearing on whether she would file charges against George Zimmerman, the neighborhood watch volunteer who has said he shot the unarmed black teen in self-defense. Corey could still decide to charge him with a serious felony such as manslaughter which can carry a lengthy prison sentence if he is convicted.
A grand jury had been set to meet Tuesday in Sanford, about 20 miles northeast of Orlando.
Corey has long had a reputation for not using grand juries if it wasn’t necessary. In Florida, only first-degree murder cases require the use of grand juries.
Corey’s decision means she doesn’t have to rely on potentially unpredictable jurors, said David Hill, an Orlando criminal defense attorney.  (read more)