Does anyone have info on medications or Melatonin for insomnia in a dementia patient?

My mom was prescribed a very small dose of Lorazepam for extreme anxiety/insomnia during bad spells of sundowning (specifically during the full moon when she would be awake until 3 am with a lot of agitation). But now she just has general insomnia - she won't fall asleep and keeps waking up until around 2 am when she finally falls asleep. She doesn't have anxiety, so I don't want to give her the Lorazepam, but I'm not getting any sleep. (I sleep with her so I can take her to the bathroom in the middle of the night.)

I know about trying to limit naps during the day, exposure to sunlight, keeping busy with activities, regular wake times, etc. That's not really working. She gets sleepy on the sofa in the evening, so we go to bed around 9:30pm but then suddenly she's wide awake. Thoughts?