Reach out to the IRS (be sure to have a properly completed Form 2848, Power of Attorney) and explain the situation to them. You can contact them at 1-800-829-1040.
They can explain the options. If there was no withholding of tax from the IRA distributions during the spenddown, this could complicate things as it could be seen as a way to evade paying tax. However, I think this is unlikely.
The most likely result will be that they may garnish Social Security income as part of the collection efforts and eventually may place the account in Currently Not Collectible (CNC) status. By statute, the maximum levy that can be placed on Social Security is 15% of the benefit.
If collection notices are received, be sure to respond to them via the method indicated in the notices.
**Say "Thanks" by clicking the thumb icon in a post
**Mark the post that answers your question by clicking on "Mark as Best Answer"
