Read the prologue and it seemed a little disjointed. It did not really sound like a diary, for one thing, but simply a first person narrative. It seemed a little jumpy, and the necklace thing seemed a little random to me. The protagonist carefully points out this necklace, but as far as she, or the reader, knows, it is of no importance. It just seems strange she would talk about a woman prophesizing doom, and then immediately after comment on a necklace in the store.

When she goes home, it's not really that weird to have two messages on your answering machine, but that's fine, it doesn't matter. Still, I felt that you just threw her whole family story in that one paragraph. Let the reader learn more slowly, particularly in a diary situation. No one has to remind their diary of their current situation; for example, her dad leaving the family. She would not be telling her diary this now-she would have already written about it likely when it actually happened.

It's also unlikely that her aunt and uncle would just say, "Wow. No room for you at our house. You're on your own, kid." Unless they hated her guts, they would at least let her sleep on the couch. No sane adult lets a kid live alone with their parents' money.

It's a good first try, but go back and revise, revise the prologue. If you like what you have written, at least don't make it a diary entry. She sounds like she is talking to someone for the first time, and usually with a diary, this is not the case.