I don't think you know what you are talking about. An eyewitness account is subjective. They could say that they believe Zimmerman transformed into a miniature Godzilla, and that is their eyewitness testimony. They say what they BELIEVE they see/hear, and that is why eyewitness testimony is faulty.
However, there is no CORRECTING witnesses. A police officer simply cannot alter or attempt to influence eyewitness testimony. Nobody can. An officer while taking a statement may attempt to clarify, e.g. "Wait, sir, you said Godzilla, correct? Or did you mean Mothra?" in order to make sure they record the statement correctly.
If she said she heard Trayvon crying, that is her statement. The court proceedings will figure out whether she can truly identify who was crying. Until then, anything else is conjecture.