Just my .02
You should press charges. Accountability is a very important piece of the puzzle for the addict to possibly decide to clean it up. Allowing your niece to go to cushy rehab as opposed to jail is enabling because you are alleviating the accountability from her actions stemming from her addiction.
She isn't going to rehab because she wants to, she is going because its a much better option for her than jail. You think its going to be effective under these circumstances? And btw, who says she is going to stay? She walks in she can walk right back out.
My neighbors son is in jail right now on 5 felonies. This kid has been bailed out and out and out. Sure enough he ended up the one of 3 places A's go, rehab (he's been in 3), jail, or dead. He was not able to get bond because he got busted for marijuana possession last year and then skipped court. He called mommy crying and wailing 'get me out mom I'll go to rehab"!! Uh Huh I bet you will. He will go to Court end May so he is in for a couple of months before sentencing. They put him in detox when he first got there (xanax, dilaudid, alcoholic, weed, meth). He is in an addiction program there now.
In our State he will be able to plead under the first offender rule and if accepted he will receive 5 years probation. During that time his file will be sealed and he will have very stringent rules including drug testing that he will have to adhere to for 5 years. At the end of the 5 years if he stays clean his charge will be expunged.
Clipping someone's freedom is about the best kick in the a** there is. Certainly there are people that come out of jail and continue their lives as they were before, but for some people its the wake up call they need.
I know this is difficult with your sister. Sister shouldn't have left daughter with mother. You know it, I know it, everyone knows it. 3 people agree, including her father, that she should face the consequences. Why does the enabler get a vote, or rather why does the enabler's vote outweigh 3 other people? You should think about that. 3 weeks rehab? I'm sorry but why not send her on vacation and maybe she can find herself.
I'm very sorry for this predicament and what someone's addiction has done to your family. If it were my niece I would send her to jail in a heartbeat if she did that to my parents. If she did it to her own mom then that's their decision on how to handle - its a whole family issue now.