What should you do if a private student loan lender files a lawsuit against you after you've filed for bankruptcy?

A listener writes in about National Collegiate Student Loan Trust collecting on a private student loan that was included in her bankruptcy filing. She repeatedly told them that the debt was discharged in her bankruptcy, she wrote them letters, sent copies of her bankruptcy paperwork, gave out her case number and her bankruptcy lawyer's phone number. Three years later she was served with a lawsuit for collection of the private student loan.

What, she wondered, should she do?