Amber Hilberling was found hanging in her prison cell on October 24, 2016. The 25-year-old was serving a 25-year sentence after being convicted of second degree murder for the death of her husband, Josh, who fell through a window to his death from the 25th floor of their high-rise apartment. Police claim Hilberling, who was 7 months pregnant at the time, pushed him during an argument, although she said it was self-defense.

WATCH: Amber Hilberling’s Mom Describes Her Daughter’s Behavior Before Suicide

The Medical Examiner has ruled Hilberling’s death a suicide, but her parents, Rhonda and Bryan, say they are not convinced their daughter took her own life. They say when they talked to her the night before she died, she was talking about the future and celebrating the holidays with her now 5-year-old son.

“I don’t know if it finally just got to her and she snapped, or if someone killed her,” Rhonda tells Dr. Phil in an exclusive interview airing Monday.

The parents claim that they didn’t learn how their daughter died until hours after her death and numerous phone calls to the correctional facility. They also claim they were not able to see their daughter until five days after she died, and that the prison still has not given them any details about her death.

WATCH: Parents Of 25-Year-Old Who Died In Prison: ‘We Found Out That She Hung Herself On The News’

In the video above, Rhonda and Bryan explain why they believe Amber may have been the victim of foul play.

Watch more from this episode here.

The Dr. Phil show reached out to Terri Watkins, the communications director for the Oklahoma Department of Corrections, and she responded to the allegations made by Rhonda and Bryan. While she declined to give an official statement, she adamantly denied that Amber was abused by the staff at the Mabel Bassett Correctional Center in McLoud, Oklahoma and said every individual in their custody is treated with respect and care. She also denied there was any cover-up in connection with Amber’s death.