I got a question about probate?

My mother was supposed to receive a certain amount off of her mother will and her mother had put her brother as the executive and she had gotten loan off the will. she had received it but when she went to get the rest of her earnings from the will that was her's her brother had put a block on her share so she cannot get any more loans on it and it is still probate. how can he keep her from her own share that was her mother promise?? and she had put in the will that if she had faught him she will get nothing?? how can we go about can we sue him? for the rest of her share??