The short answer to you question is that you have no legal obligation to pay your parent's debts.
Stop Using the Cards Immediately
It is important that you no longer use the cards. Cut them up. Call each creditor and explain that your parent passed away. They may want to see a copy of the death certificate. If so, provide them with one. (It is a good idea for you to make multiple copies, in case you need to send it to different places).
Responsibilities of an Authorized User
As an authorized user, you do not have the financial responsibility to pay her bills. The responsibility resides with your parent's estate. If you used the cards for your own purchases, that may change the analysis; you may have an ethical responsibility to pay the debt, but not necessarily a legal obligation to do so. To know your legal obligations it makes good sense to speak with an attorney. If an attorney was handled her estate, that is a great place to start. Did your parent have a will? Did the estate go through probate? Did your parent leave any assets to be inherited, whether cash, investment accounts, or real estate? If the estate has assets to pay the debts, then it must do so.
Consult With an Attorney
If an attorney handled the estate, you should ask him or her exactly which steps need to be taken. Make sure the attorney is aware of any debts that you know about. If you are going to speak with an attorney, which I recommend that you do, you should do so even before you contact the creditors. No matter what, as I mentioned earlier, make sure the cards are not used any further.
For additional general information, see the Federal Trade Commission documents Paying the Debts of a Deceased Relative: Who Is Responsible? and FTC Issues Final Policy Statement on Collecting Debts of the Deceased.
I hope this information helps you Find. Learn & Save.