Bank account

My mother owns a bank account with a very large amount of money. She lives with my brother and his family because I am single and travel frequently for my job. She is very old and in very poor health. Due to pressure from my brother, she designated him as the nominee on the bank account. It is her wish that after her death the money in the bank account be divided equally between my brother and I. But she also worries that my brother will just take all the money and not give me anything. She has overheard my brother plotting with his wife to do the same. I am also worried that after my mother's death, my brother will simply take control of the account and electronically or otherwise transfer all the money to his account. I understand that there is a recent Supreme Court decision prohibiting a nominee from owing all the money and that a nominee's role is merely to distribute the money to all legal heirs. However, if my brother takes all the money, I would have to go to court to get it my share which could take many years. What can I do to prevent my brother from taking all the money after my mother's death?