File MFJ and fill out an innocent spouse form 8379 to send with your 1040. This states that your part of the refund, based on some arcane calculations, will not be intercepted, but the part that is hers.

From IRS:

"Did you file a joint Federal tax return AND did the IRS take your refund to satisfy your SPOUSE'S OR FORMER SPOUSE'S past due Federal tax, child support, or Federal non-tax debt, such as a student loan?"

You are eligible for innocent spouse relief... unless you are in a community property state such as California.

I hope this helps.