If she worked and had an insurance policy through her employment, and kept it in force after leaving, contact the human resources department to get information on their carriers.
You would need to dig through your Mom's papers or look in her safe deposit box at the bank [if she has one], or if she kept check registers from the past go through each one to see if she paid an insurance company.... otherwise I wouldn't know how else to track down if someone had an insurance policy. Maybe someone else on the forum would know.