In consideration with this requirement, it can be stated that Sally cannot sue Mary. However, Sally can insist or try to convince Mary personally, but she cannot file a case against Mary under law. The general rule of this particular law is that the testator cannot be enforced particularly by the promisee if the testator later on conducts an action for revoking or superseding the will that had been made (Dobbs 2002). Promisee only has the right to sue the estate of the testator for breaching the contract. This provides protection to the freedom of testator for disposing off his or her property as he finds it appropriate.
The basic rule for this contract is that the terms and conditions involved have to be definite and certain and the establishment has to be done in an affirmative manner by a convincing and clear testimony (Burrows 2009). This is a compulsory requirement. Therefore, as no legal testimony has been formulated in a convincing and clear manner; Sally cannot take legal actions against Mary. Even if she provides the series of letters as proof, it will not be sufficient. This is because it is not a proper testimony and has not been signed by both the parties involved, Mary and Sally.
If there had been a legal testimony formed, the case would have been different. In such a situation, as the testimony would have been in written form and signed by both the parties, Sally could have sued Mary for her property. Sally still could not have sued Mary for the obligation that she will be staying with her. In such a situation, Mary will be having the opportunity to enjoy her freedom and Sally cannot present her in front of the court.