Can't you seek help? Can't you find a lawyer to send her a letter reclaiming your money, together for the reasons why the money is yours and not hers?
I'm afraid that if you are so scared she will silence you quickly and then it will be more difficult to bring up the topic again.
If you feel you are not alone in this and that someone can speak up for you, you'll feel better.
Can you call any part of the family on your father's side for help?
Alone we are often lost. In company things get better.