Contact your local Bar Association (lawyer's oversight group) and your state's Attorney General's office to ask for help.
If the attorney represented your mother, she may have no obligation to you at all. Unless you are a party to the lawsuit and represented by that attorney, the attorney should not answer to you.
Any settlement in a lawsuit might go to your mother's estate. If you are represented by an attorney in the estate, speak with your attorney. If the probate court has appointed an executor or administrator of the estate, speak with that executor or the executor's attorney on this matter.
The attorney handling the estate should inquire of the attorney who initiated the lawsuit for your mother about the status of the settlement.