River went to prison for a crime she didn't commit, as we now know. So, she's consigned to spend her life in jail, so the Doctor can fly under the radar.... which he ends up not doing anyway. It's not about whether she can escape on her own or not - it's about the fact that the whole reason she's there in the first place is to protect the Doctor by continuing the facade that she killed him and that he's dead. Except he isn't, and based on the Christmas Special, he's made no effort to be discreet about it.
Then when River finally does die, her ultimate fate is to be a cyber nanny to a bunch of kids who don't really exist, not because she wants to but because the Doctor doesn't have any other way of keeping her alive after she dies.
I'd call that pretty douche-y.