Nicole Alvarez's attorney, Joseph Low IV, confirmed that his client had received a subpoena to appear before the grand jury on Wednesday. He said he did not have any more details.
He also declined to characterize the relationship between Alvarez and Dr. Conrad Murray.
Newspaper reports have called her Murray's girlfriend and said the pair have an infant son together. Alvarez's apartment was searched last month.
Murray is the target of an investigation into Jackson's June 25 death, which has been classified a homicide. He told police he gave the pop superstar the powerful anesthetic propofol and other drugs in the hours before Jackson's death.