AURORA, Colo. -- The mother of a woman considered a "person of interest" in the case of a missing Aurora girl said that her daughter had proclaimed her innocence before she died last week.

Mary Lowe said her daughter Shely Lowe had told her she didn't know anything about the disappearance of Aarone Thompson, who was reported missing in November. Police believe the little girl, who would be 7 year old, had been missing for up to 18 months earlier and is probably dead.

Shely Lowe was 33 when she died last Friday. Autopsy results are pending, but Lowe had suffered from a heart condition and police said they don't suspect foul play.

Lowe was the girlfriend of Aarone Thompson's father, Aaron Thompson, who has said his daughter left home after an argument over a cookie and never returned.

Mary Lowe is hoping for a federal investigation to look into how Aurora police have handled the investigation. She said that police put her daughter and Aaron Thompson under intense pressure without producing any evidence of wrongdoing.

Police had said that Aarone was not enrolled in school and that no one had reported seeing her in more than a year. The mattress from her bed was also missing, indicating she had not been living at home when she was reported missing.

A few days before Lowe died, police and prosecutors said the case was being turned over to an Arapahoe County grand jury, which could compel witnesses to testify. That work is expected to begin this week.