Criminal Law Questions? Ask a Criminal Lawyer.
A judge can hold your sister no bail if he feels that she is either a flight risk and/or a danger to the community. If she is already on probation, that makes it less likely she will get bail set. She can file a request for a bail review so that her bail amount, or lack thereof, can be challenged.
She's probably looking at 5-15 years on the drug charges and the child endangerment could net her 7 more years (if they are charges related to the drugs), and she can get the amount of time she is backing up on her probation. More than likely the prosecutor will not proceed on all charges but will give her some sort of package deal on a couple of the charges. I can't estimate what the deal will be because it is dependent on the kind of drug, the quantity, her entire record, the strength of the case against her, etc.
She should get a lawyer as soon as possible if she hasn't. If she can't afford a lawyer, she should sign up for the public defender or request a court appointed attorney when she goes in for her next hearing.