co-signing a loan

Hello, I am asking this question for my mother. She co-signed a loan for my younger brother to go to a Commercial Truck Drivers Training School with the understanding that if he worked as a driver the loan wouldn't have to be paid back. He decided not to become a trucker and his wife was making payments until almost a year ago. They filed for bankruptcy a few months ago and as far as i know did not include this loan on their list of creditors. Now the company is coming after my mother to pay this back and she just can't do it. I know she shouldn't have done this for him, but she was trying to help. What I was wondering,is, if they did not include the trucking co. on their list of creditors when they filed bankruptcy, is hse still responsible? She lives in West Virginia and the school is in Pennsylvania. Thank you for any answers you can give me.