Please sir how for how long is my sister supposed...

We would like to inform you that according to the Federal Criminal Law, if your sister was suspected for commiting a crime and there is no no accusation, then it is related with the Public Prosecution investigations, as the suspicion could take 48 hours and may be extended to 15 days for investigations. If that period finishes then it will be renewed to another 15 days or 45 days. If there is no accusation against her then she will be free. 
We advise you to hire a lawyer to follow up the case file and follow the legal procedures.