I am only six years younger than your wife, dave1951, so I believe your missus is in the prime of life!
When I first moved to the UK back in 1995, I was a 25 year old mother of a three-year-old. However, I didn't make any friends with other parents. I knew the child-minders of the children. Once I could work (I was on a fiancée visa), I did but even then, it was simply a matter of having work colleagues and no real friends. When I had my second child, I became a stay-at-home parent. At that same time, my husband became a telecoms contractor and moved to Europe. He only returned to England 72 days a year. It was very hard for me because although I had only one sister, I have 72 first cousins and I saw them every single week back in Texas. In my last US job, my workmates were my extended family. In fact, two workmates are my children's godparents. Add the fact that this was a time before social media or Skype and email was the closest thing you had to swift communication, it was an extremely lonely existence. I did suffer from post natal depression after my second child was born and the feeling of isolation didn't help, I had to go out and make my own life.
I didn't go to college in the US so I went on an Open University course. It was the best thing I ever did. My instructor introduced me to a few of his other students and we would meet once a week for a coffee. We had a commonality and later we started to hang out together and they are still my friends. It boosted my confidence, I got to understand the people a bit better, my husband's absences were less stressful and I got a UK qualification.
My husband moved us closer to his parents 200 miles away and I had to start the process all over again. This time around, the internet really took off (2000) and I started connecting with people who shared my interests and we met regularly. Plus, I also started a home-based business when my third child was born. I got to travel the areas around Greater Manchester and meet all sorts of different people. Many started as customers and when I left the UK five years later in 2004, became good friends.
My husband is still a telecoms rep and moved us back to the US but we moved to five different cities in three different states in four years. I've had to keep starting over and over. But in this day and age of technology, meeting new people is so much easier. There are groups for everything. I've taken a few courses at the local college, joined a women's group who travel to cities around the US on weekend trips, I started another home-based business (I haven't worked outside the home in 19 years) and a host of other things. I'm returning to the UK indefinitely in 2019 and I will do that process all over again and I'm quite excited. To me, I think it's all a state of mind. If you think it's hard to make friends than it will be quite difficult. I guess for me, I had to make a decision to make the best of my situation. Sure, I've had some difficult times with unbearable loneliness but I chose to find a way to make it better. It's very sweet that you're concerned for your wife but I think you being with her and helping her find her way around will make all the difference.