To the extent the prosecution uses her to testify to a declaration that Trayvon made in order to prove the matter asserted in the declaration that would be hearsay. Such as "Trayvon told me on the phone it was raining" in order to prove to the jury that it was raining.
An example of such a statement I expect the prosecution to introduce would be her testimony that Trayvon told her that he was being followed, in order to establish the fact that Trayvon was following her.
Nevertheless, even though some of these statements may be literally hearsay, I expect the court to allow all or nearly all of these statements into evidence under the residual exception if necessary.
I meant to write “in order to establish the fact that Zimmerman was following Trayvon”.
What I recall reading is, she said the call dropped before she heard anything other than words being exchanged.
If Zimmerman initiated the fisticuffs, she should have heard quite a lot, judging by what turned up on the 911 audio, recorded from much further away.
On the other hand, if Martin pressed End before setting about messing up the Man, she would have heard just about what she heard.