Check out the comments section. The poster types very well and does have the paranoia but outside of that I don't think it's one of her meth friends. However, what she stated in the last(2nd) message she made is more than likely what happened to Brandi.
"Obviously I hope this isn't what happened, but not just in the movies, in real life too.... if there WAS some sort of plea bargain and Brandi turned in a bunch of dealers, well it's not rocket science to drug dealers that if somebody gets busted with large amounts of drugs, not to mention the high speed chase, and they get off with a slap on the hand, even if there was no plea bargain and it was just her uncles status in the dea that saved her, the drug dealers don't know that, they just assume if you got off easy then you ratted someone out."
She brings up a few good points about what Brandi had, how she was arrested, and I can see how shocking it would be for her to be out on probation just days after finding a zone of meth after a high speed chase, she more than likely would have been DUI for it as well. That is not going to add up to your meth dealers - and while I won't point fingers, whatever friends house she went to, should be the first place they would have went looking for any physical evidence she had been there (clothes, cd's, IDK whatever she pretended she was going over there for)
The call days later about her murder and the wait for weeks until filing the missing persons is probably just parents being naive, but then again no one has ever called my family to report I was in the lake murdered. Really interesting case all in and of itself.