1. Since your mother has executed a WILL bequeathing the entire property to your brother, was the WILL executed by her when she was of sound mind then its a closed matter. If your mother has executed the WILL when she was of unsound mind or she was made to execute the WILL by your brother in his favour through coercison, force, fraud, then you can challenge the execution of WILL by your mother in an appropriate court of law.
2. Based on her unsound mind, if your brother tries to take VRS benefits of your mother, you also stake a claim from your mother's employer. You can inform her employer about your stake in her VRS benefits as she is of unsound mind and you are her daughter and request the bank not to disburse your mother's VRS benefits without your knowledge.