Unfortunately to contest this will be expensive and time consuming. However, if you are going to do anything you need to do it now and get a deposition videotaped with your mother before she gets any worse. Your claim will be undue influence. The problem is that the attorney is not going to be on your side since that would also make him liable. The court will tend to go with the attorney's testimony since he is an officer of the court.
Your case will be stronger if your mother will agree to join in the suit.
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