If you die without leaving a valid will, money and other property you own at your death will be divided and distributed to others according to your state's intestate succession laws. These laws divide all property among the relatives considered closest to you according to a set formula. Your stepmom won't inherit from you unless she legally adopted you or, in some states, tried to adopt you but couldn't. Or, in some cases, stepparents may be permitted to inherit if they can show that they had a long, close relationship with their stepchild -- highly unlikely in your case.

Despite the fact that your stepmom is unlikely to get any of your property under your state's intestate succession laws, here is my advice to you: Write a will at once. That way you can be sure of where your property goes.