Your wife has two things going on here. First of all, the new arrest will violate her on probation. That means that probation can ask for her to be resentenced to time, since she's not been a successful probationer. The judge has the power to restore her to probation if probation is looking to revoke her, but he also has the power to sentence
her to anything up to the maximum for the crime with which she was charged. So she could do a year in jail on the violation.
The third misdemanor shoplifting offense in Missouri gets bumped up to a class D felony as you have rightly already said. There's no mandatory minimum time required, but the state is not going to see her as the world's best probation candidate. The worst case scenario on the new charge would be four years of state time, which would absorb the year of county time which would be the worst case scenario on the violation of probation.
The key to this is a good lawyer. It's unlikely that her case will be reduced because the law of your state mandates a felony charge for the third theft
offense. It would have to be reduced to a non-theft offense, and as I don't see one in your fact pattern, it's unlikely it's going to be offered. Your wife has also made matters fairly difficult for herself by her inability to stay out of trouble, but her physical and mental health issues are in her favor. That is, they won't make the offense go away, but they do open up options such as mental health court
, just as an example, an alternative sentencing program where a defendant works with the court on addressing her health problems as well as her behavior. It's a form of probation but intensively supervised, and, if she meets eligibility requirements, such specialty courts are available in Missouri.
House arrest is still another real possibility, given her issues. And, of course, while you don't have to leave the store with the goods to be charged with and even convicted of shoplifting, she could also fight the case if her lawyer thought that she had a viable defense to the charges.