Could the alimony in question that the ex-wife received be taken back?

If I understand your point correctly, the ex-husband was convicted of some kind of fraud/Ponzi scheme, and he used some of the money he improperly received to pay the ex-wife's alimony payment. The short answer is this - if the people who are owed the money come looking for it, the ex-wife will probably be ordered to pay it back. That's too bad, since she did nothing wrong, but it wasn't his money to give. She'll need a good attorney to see if this can be fought off or not. I'm guessing not.