Unfortunately, the credit card company can come after you for the debt even though your mother filed for bankruptcy.
The moment that your mother put your name on as an authorized user you became responsible for the debt.
This is the trick of the credit cards. It is a fall back for them, and it happens more than you would think. Your mother doesn’t have to pay the bill but you do.
Of course you could refuse but then they would ruin your credit as a result. You might want to try to settle with them for a reduced amount of the balance.
A side note, because your mother has defaulted on the debt and filed for bankruptcy this credit card has probably reported this on your credit report, so settling may be your best option to get rid of it.
best of luck.