How can someone sleep while hearing voices from PTSD?

I have a friend who tells me she has trouble getting to sleep every single night. She has tried having audio books play softly in the background, guided imagery like counting sheep or imagining beaches, taking melatonin, masturbating, etc. She says she hates warm milk for some reason.

She says she hears voices which torment her all the time, and that it's not schizophrenia but PTSD. These voices often make it impossible for her to focus on anything or sleep. So I'm wondering, does anyone have any suggestions for sleeping that pertain to this specific condition?

By the way, she also says she has panic attacks at night that keep her awake. The voices and the panicking are directly related.