http://encyclopedia.adoption.com/entry/inheritance/186/1.html
"Inheritance
Although it would seem logical that a child adopted by nonrelatives would inherit from the adoptive parents and not from birthparents (and indeed this is true in most cases), there are many ramifications of the laws regarding inheritances, and statutes vary from state to state.
Generally, an adopted child inherits from adoptive parents and may not inherit from biological parents unless specifically named in a will; however, in the states of Colorado, Louisiana, Rhode Island, Texas, Vermont and Wyoming, the adopted person's right to inherit from birthparents and birth relatives is retained.
In some states (for example, Kansas, Mississippi and Oklahoma), whether or not an adopted person is excluded from inheriting from birthparents is not addressed while in many states the adopted person is specifically excluded from inheriting from birthparents.
Although an adopted person may inherit from adoptive parents, whether or not the adopted person will also inherit from adoptive grandparents is not always clear and depends on state laws.
It is best to review current state law and consult an attorney in the event of a question or a desire to provide an inheritance for an adopted-away child. (Two legalistic terms used when discussing inheritance are "adopted-away" and "adopted-in." An adopted-away child is a child who is born to a family and then leaves the birthparents because of adoption. An "adopted-in" child is a child that enters a family by adoption.)
If the child is adopted by nonrelatives, inheritance generally must come through adoptive parents; however, as recently as 1986, a challenge was made to this assumption in New York. Jessie Best wrote her will in 1973 and provided for her assets to be given to her "issue." Her daughter had given birth 21 years earlier to a son who had been adopted by nonrelatives.
The executor's of Best's will discovered the existence of the adopted child. With the permission of the birthmother, who also had a child born within wedlock, the trustees asked the adoption agency for identifying information since the adopted adult might stand to inherit a considerable sum.
The adoption agency told the adoptive parents, who disclosed the son's legal name. When the birthmother died in 1980, the trustees asked the court to determine whether the adopted child would share in the division of assets with the child born within wedlock and not adopted.
The court decided the adopted child was "issue" and could inherit; however, the court of appeals overturned this decision.
In a very unusual case, adopted adult Cathy Yvonne Stone alleged she was the birthdaughter of Hank Williams, the late singer. Stone sued to receive part of the royalties accruing to Williams' estate. Her suit was rejected at a lower court level, but, on appeal, a federal court decided she was entitled to have her case heard by a jury. In 1990, the U.S. Supreme Court affirmed this decision. In addition, the Supreme Court refused to overturn an Alabama Supreme Court decision that decreed Stone was a lawful heir to the estate of Williams.
In the case of a STEPPARENT ADOPTION, the adopted child may inherit from both birthparents and the stepparent in some states, but in other states, the adopted child may only inherit from the custodial parent and stepparent. (See STEPPARENTS.) Author Anne Wiseman French wrote, "In stepparent adoption situations, many states' statutes mirror New York's law before the 1987 amendments and preserve the child's inheritance rights only from and through the biological parent having custody of the child. Other states, however . . . preserve the child's inheritance rights from both biological parents."
The intent of the donor is significant in determining whether an adopted child may inherit, and how intent is determined varies from state to state.
Anne Wiseman French, "When Blood Isn't Thicker Than Water: The Inheritance Rights of Adopted-Out Children in New York," Brooklyn Law Review, 53 (winter 1988): 1007-1049.
Joan Hollinger, ed. in chief, Adoption Law and Practice (New York: Matthew Bender, 1988).
Timothy Hughes, "Intestate Succession and Stepparent Adoptions: Should Inheritance Rights of an Adopted Child Be Determined by Blood or Law?" Wisconsin Law Review (1989): 321-351."
Also, if she did have a will, unless the will is challenged as defective, the will would determine who inherits