One of the main things to understand about bankruptcy is that is does not discharge debts, but rather the personal obligation to repay the debt. The debt is "still there." It exists, but you and your wife have been discharged from having to repay it. You could repay it, nothing forbids that, but you can not be asked to repay it and it cannot be enforced against you.
Your mother-in-law, however, did not go through bankruptcy. She was not discharged from her repayment obligation.
You can assist her by having her write to the collection agency and telling them she does not want to be contacted further or you can find a lawyer for her. If a collection agency is informed that she has a lawyer, they are required to direct all further communications to the lawyer.
Answered on Aug 10th, 2011 at 5:50 PM