I assume she is of age and is is effectively looking to retire in the US?
9 FAM 502.2-1(C) Conferring Immigration Benefits to Family Members
(CT:VISA-1856; 10-23-2023)
a. Immigration Benefits from Adult Children Only: Only U.S. citizens aged at least 21 years may confer immigration benefits on a parent or parents.
b. Parents or Siblings of Adopted Child:
(1) Biological Parents or Siblings: An adopted child (as defined in INA 101(b)(1)(E), or (G)) may not confer immigration benefits upon a natural parent or sibling unless such adoption has been legally terminated. This is true even where the child never received an immigration benefit based on the adoption.
She should look at other options.