Yoga & mindfulness can help if she lets them; so too can a good long walk (60 minutes a day at least), a run, some sort of exercise that gets her puffing. Also something that's not on a screen, but is about being in the moment: reading (a book), painting, playing a musical instrument, singing in a choir ...
Then sleep hygiene:
Go to bed at pretty much the same time every night, and get up at pretty much the same time (7 days, don't change too much for the w/e)
Dark room, eye mask & ear plugs if necessary
Cold room, warm bed (the window open a little can help even on these cold nights)
No screens for at least an hour before bedtime. Radio or soft music if necessary
Read to sleep
Breathing & relaxation exercises: the simplest: focus on breathing in long & deep through the nose and out through the mouth. Focus on nothing but breathing in and breathing out (yoga w/o the physical posture - yoga is really about the breathing).
And the thing that can really help but may feel counter-intuitive: don't get too stressed about waking up in the middle of the night, or about not sleeping. Lack of sleep won't kill you. But stressing about lack of sleep will make the effects of lack of sleep worse.
It's a difficult time for her. There's no instant cure. It will get better, but she'll just have to plod through the difficult bit. Step by step, moment by moment, breath by breath. It's awful, but it will pass.