Insomnia after 3 hours

Hello
My Mum (78) wakes after about 3 hours and can’t get back to sleep. She says she has too many thoughts, head too busy and in particular she’s been unable to sleep due to thinking about people who have passed away. She feels the heat, so I’ll only sleeping with a bedsheet on and fan on even in winter. She has deep dark circles under eyes, puffy bags and is exhausted. It’s been like this for many many years, always being a poor sleeper but it’s worse now than ever. She had Breast C 2 years ago with radiation treatment. She is of heavy status but not terribly overweight, carrying weight around her middle more than anything. She cannot sleep during the day, is a light sleeper at night hearing the smallest sounds, can’t handle any light in the room. She doesn’t drink, has weak black tea in the morning to lunch time but nothing but water after that. She has a sensitive stomach suffering diarrhoea often from the smallest thing she eats. I have sent her some info on homoeopathics for sleep and she says coffea sounded a bit like her. Would you suggest this or something different for her to try? She’s tried melatonin but it only helps to get to sleep but still wakes after about 3 hours always around midnight-2am
Thanks