@Pamela Rosa,
That this young woman may have cognitive problems, or learning disabilities, that affect her literacy, or ability to read and write in cursive, in no way discredits her testimony regarding her phone conversations with Martin, or what she heard between Martin and Zimmerman.
Nor does the fact that she may have dictated a letter, that someone else actually wrote for her, mean that she didn't author the letter.
And the revelation of her literacy problems, in such a public way in court, must have been terribly humiliating for her. It also may have aroused sympathy for her in the 6 jurors, most of whom are also mothers.
The fact remains that her account of what Martin said to her, and what she heard, sounds credible and authentic. She describes Martin as fearful and concerned about the man who was watching and following him, and he was trying to get away from that man. She describes hearing Zimmerman confront Martin in a challenging manner--without in any way identifying himself to Martin, and the last thing she heard Martin say was, "Get off me," suggesting Zimmerman was the aggressor. And she was consistent in this account. And she held her own on it, even under cross-examination.
Nothing else about this witness matters except whether the jury believes her account of that last conversation with Martin and what she heard between Martin and Zimmerman.