Call the police and inform them you believe someone to be acting in fraud. Then talk to your lawyer and get the relevant documents (she will have to prove for example with a marriage certificate); it is also probable that she is not legally able to do anything with the estate.
Why is there a dispute? Was there a will? Was the estate of the parent probated?
When a life tenant dies the life estate is extinguished. A death certificate should be recorded in the land records.
Sounds like there is controversy over the estate. Only one of you should have a letter of authority from the court.
A Life Estate provides its owner with the use and possession of real property for life. The life tenant can extinguish that right by executing a release that must be recorded in the land records. Otherwise it is automatically extinguished upon the death of the life tenant.
You should be able to get a copy of the death certificate from the town clerk's office in the town where your mother died.
The funeral expense is one of the the first expense that must be paid in the statutory scheme of debt paying that executors must follow. If the executor hasn't paid that debt they risk personal liability. They should be reported to the court that appointed them. An incorrect name on the death certificate should be reported to the authority that issued the death certificate.
How much it would cost to open an estate for someone that has died will depend upon the attorney that you hire. It is very hard to open an estate after someone has died. Estates should be started before a person dies.
The will should specify who should inherit. If there is no will, the state will have a law that specifies. Just because someone is related does not mean they are entitled to a portion of the estate.
A lawsuit commenced against a person can continue against his estate after his death. The attorney for the plaintiff's estate should have filed a notice in your father's estate that there is a claim against the estate.
They will look to the wording of the will. It should specify whether that share goes into the general estate or to the deceased named person's estate or heirs.
You will need to provide some proof of your relationship to the decedent when you file a claim against the estate. You should consult with an attorney who specializes in probate law who could review your situation and determine what your options are. She would also know how you can establish your relationship to the decedent.
If you are dealing with the estate, then banks, building societies, Local Government will ask you for sight of death certificate. Only then should it be sent - AND IT SHOULD BE A PHOTOCOPY which you send.