It matters not who resided in the home but who owned the home. If the foreclosure and refund happened during the time that the home was owned by both parties, then she has a CP interest in the refund. There might be credits or reimbursements owed but there aren't enough facts to determine this. Seek legal counsel. If the refund wasn't that large, say a couple thousand dollars, then it might be more financially sound just to split it with her then to pay the litigation costs of the refund check.
Seek legal counsel, it is likely that Mr. Benton is correct. You continued living in the house and those payment would likely be in consideration of fair rental.
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If the property was jointly owned and not resolved by the divorce settlement, you will need the court to decide how to resolve the issue if you cannot reach a written agreement. Are the proceeds sufficient to justify a fight and the expense of a motion in court, probably with an attorney. There are issues involved in the court's decision that include fair market rental credit against the person who occupied the house post separation, credit for maintenance expenses and mortgage/insurance/tax payments. I suggest discussing these issues with an attorney in person to review the documents.
The comments made here are meant to direct you to receive local consultation from an attorney in your area and ask proper, detailed questions to get the best legal advice upon which you can take appropriate action.