Mari is ready for school in case of default. We filed joint taxes. They kept restitution to the state. Can she keep Federal reimbursement

Yes they will, you can file a form 8379 injured spouse claim to allow your party refund free of debt here is a link to the form, if not sent with the return it will be approximately take 6 to 8 weeks to process http://www.irs.gov/pub/irs-pdf/f8379.pdf You fill in the form that you are the injured spouse