How can the state dismiss conspiracy to commit shoplifting for 2 of 3 co-defendants?

The two that talked about doing it are married and the third had know clue that they had done (shoplift) what she attempted to do had she known when given the chance to leave in truck that had their stolen items she would have , that being one in many of the facts to support she did not know that they were doing anything other than get some groceries the reason she even stopped there on her way to go visit family she don't see cause she lives out of state.