Hey mumski, big hugs, it will be hell the first few months. My husband died in May 2016 and my daughter had to go to Canada in August for her international degree year in the August. We were both so grief stricken and numb I hadn't even organised any Canadian dollars for her, it was a terrible time. I did go over and surprise her for a 5 day visit.
What I've realised, all these years later, is that she didn't want to worry about me being on my own as she was having a great time and starting out on her own young adult life. Initially when she rang I hadn't been doing very much and had no news, I could tell she was disappointed I didn't seem to be making the most of my new 'me time'. I made a great effort and started volunteering at a local charity shop, travelled and socialised more, and did some courses (had to pay for them, wish I'd appreciated the 'good old days more when they were free!) I always had something positive to say when we spoke.
I hope her move goes well and they get on well living together again. When she goes you can start experimenting with new things. You could try new recipes you've found (something your late husband wouldn't like), go to a painting class, get a bike, join a rambling group - so much to do and new people to meet who might share your interests. I won't say get a dog, I've got to go out in the freezing cold again in a minute!
Be happy