Are card holders on an account reliable if the card goes to debt collectors?

If you were solely a signer on the card and not the actual account holder than your mother put herself as responsible for not only what she charged, but also what YOU charged. If it became overwhelming it was because the TWO of you spent more then she could afford to pay. You may not be liable for the bill, but your partially responsible for the predicament she is in and her ruined credit.