Most of the answers are bull**** but... here may be a little help
First, ignore most of the answers. They are suggesting your wife should have done something diffrent or that you are at fault because they dont like you. Silly people.
The demand for $200 is a standard Wallmart ploy. It's a form letter.
1) What they are doing may be iligal in your state. They are demanding $200 or thretening prosocution. Unless you signed an agreement with them that states you will give them $200 then they are probably guilty of extortion.
"Give me $200 or I will break your legs" is extortion. "Give me $200 or I will take you to court" is still extortion. Some states have spicific laws baring lawyers from thretening a criminal prosocution to gain advantage in a civil suit. You may do will to address your letters to their legal department and not the loss prevention department.
2) Write their legal department asking for the basis of the demand. Ask for a copy of any contract between you, the person named in the letter, and their orgnization. Send it registerd and certified mail. They will probaby not respond but it will be usefull if you ever get to court. It will show you were making a good faith efort to reslove the situaton.
3) Ask the police department records section for any record they may have of the incident. They should be able to look it up by month and name. If Wallmarts loss prevention called them there should be a record. If there is no record you stand a good chance of beeting any state prosocution. They probaby did not call the local police. Loss prevention or the mall security are not the local police. With out a timely police report the local prosecutor is not going to touch it. That leves Wallmart with only the option of filing a civil suit. A civil suit, even if you lose, dose not go on your criminal record.
4) Sounds like they are making an offer to settle a potentual civil suite against you, before they file the suit. Ask them for that offer in writing, naming the parties involved, the amount they request, and exactly what they are offering to do for that $200.
5) Also ask them for details on what civil suit they think they are bringing and whom they think the defendants are. They would look silly taking a 12 year old to court.
If your wife did not exit the store with the goods they would have to bring a verry complicated case involving aleged conspircy before they could even attach an adult to the list of defendants. They would have a very hard job proving the conspiricy.
If they are not prepared to answer then consider talking to legal aid. They will probably not help you untill an acton has been filed in the courts but they my be able to refer you to some one who can help.
Consider finding a law student or professor to help you figure out if they have any legal basis for demanding the $200. Shoplifting is bad but this is America. They are not the judge, jury and collection agency. They don't have any legal claim against you unless you signed an agreement with them or a court decides in their favor.
Ask them for the legal basis for the claim to the $200 and copies of any documents that they have to support the claim.
Now do one last thing. Get your wife to write down everyting that happned, in order. Incude any thing they said. For example, did they say she could not go home unless she signed a statement? Did they say she would be turned over to the police unless she signed a statement? Did they detain her untill the real police arrived or just long enough to get her to sign a document?
While it's legal in all states for security to detain a suspected shop lifter, they can only detain them to asitern their identity and to recover any goods, and then can continue to detain some one until they hand them over to the police. But in that case they must call the police prompty. They can decide that they dont want to call the police, at that point they must let the person go. In most states they are not allowed to detain you for the perpous of extracting confesssons or getting you to signe documents. That's kidnap with extortion. Any confession your wife signed, while under duress, and that was not made of her own free will, and in her own words, will stand little chance in court.
So type out a full history from your wife, with date and times. Do not send that to them! Do wite to them by certifed letter and ask for the information outlined above.
Remember, this is a game of bluff. They would like $200 to go away. You want them to go away. They can't afford to take you to court to get the $200 and it would cost you more than $200 to hire a lawyer to defned you self. You may want to offer them $20 to go away. You may want to find other people who have been extorted in a similar way and take a group of plantifs to a lawyer.