Disclaimer: The materials provided below are informational and should not be relied upon as legal advice.
So long as your niece is on probation, it would not be advisable for her to leave the jurisdiction. Be sure to consult your own attorney to protect your legal rights.
It is difficult to answer your question without further details. Who was your niece's lawyer back when she was placed on probation? Is your niece 18 yet? Does she have a future court date at the Youth Guidance Center? Feel free to contact me at 415-782-6000 or e-mail me at firstname.lastname@example.org if you want to discuss this matter further.
Adam G. Gasner