My mother has recently been having problems regarding her short term disability insurance, and I am wondering about the regulations on such insurance policies, because for what they are doing to be legal, it makes no sense.

Here is the situation. My mother had disability insurance at her old job, which worked her until she had a breakdown and is mentally incapable of working (seriously, totally incapable). So the company pays out her benefits after putting up a bit of a fight, fine. But now she has transferred to long term disability, and they are paying that out. There is only one problem, the short term company (Unum) hired a lawyer and sued the government for back disability benefits, paying me 10770 (because I passes 18 after the time period, so it was awarded to me) and her much more. Then the short term disability insurance company (Unum) demanded back all of that money, which we paid in full.

So essentially, she paid into a policy for 13 years, and when it came time to collect on it, she did, but the company made up virtually all of its losses by getting a check strait from the government. Literally pure profit from paying out a policy, and despite this, they are demanding more money from us that we never received, and have even hired a collections agency to collect it, despite the fact that we can't possibly owe it, because we never had it to begin with.

So I guess the question is: Where can I find regulations on disability insurance, to see exactly how what they are doing is illegal (because if its not, that is terrible, and we will take the story to the news and I am sure Unum will swallow their sorry *** and pay it back), or any other possible solutions. Thanks.
Additional Details
She was not double dipping, she was getting benefits ONLY from Unum. Unum just sued the government to get free money and make a profit from paying out worst case scenario.

So essentially, she paid 13 years into a policy, and then needed it, and it got paid out to her, and then the insurance company stole directly from the government and made a profit from worst case scenario. Isn't there some kind of insurance law that says "you can't profit from worst case scenarios"???