Can your credit be ruined if you do not pay your deceased mothers medical bills there was no estate she owned nothing?

It should not affect your credit unless you signed as a guarantor on any of the agreements. In most cases the debts of the deceased, including funeral expenses, are the responsibility of the estate. The estate, or its beneficiary should reimburse any valid debtors before giving any of the assets away. Consult a probate attorney in your jurisdiction for help.