Your sister needs to talk to a criminal defense lawyer in Eureka. It sounds like one of those creative programs to work outside the due process model. Those can be good or bad depending on how they are run and the specific facts of the case. The fact that the DA dismissed the underlying charges is not a guarantee that there will not be a violatio of probation. A VOP requires only proof by a preponderance of the evidence so, even where someone is actually acquitted by a jury, their probation can still be violated.
So, she should go into this fully informed. The lawyer can tell her if they expect an admission and, if they do, will they violate her if they don't like her response. It could be a good way out -- but make sure that there are no pit falls.
Good luck to your sister!
This is not legal advice. In order to get legal advice, you need to retain a lawyer and establish an attorney client relationship. So, talk to your lawyer! [I am licensed to practice law in the state of California and am admitted to the federal courts in California, Washington D.C., the Ninth Circuit, the U.S. Supreme Court and a number of other federal Circuit and District courts. For legal advice, you need to retain a lawyer in the jurisdiction in which the matter is pending.]
If your sister is represented by an attorney she should call that person immediately to get adice. If she is not then she should speak with a local criminal defense attorney. If she cannot afford to hire an attorney she should apply for the public defender. She will want to be fully informed about her options and possible outcomes before proceeding forward. As Mr. Sanger indicated although the underlying case was dismissed she could still be found in violation of probation.