Two things are at play here.
1.) You can't force an introvert to change, or even engage. It won't happen.
2.) You and your buddy go way back. Even though you were separated, for many years, you were able to pick up where you left off, as if nothing happened.
She wasn't part of that. It makes someone, with a natural tendency to feel like an outsider, feel like even more of an outsider.
Case in point:
I married Mrs. C. when I was closing in on 60. When her siblings, or her children, are visiting, they are not only reminiscing on things I not only have no interest in, but no knowledge of happening. (Luckily, none of them seem to notice, or if they do, care about me going back to my cave, and ignoring them.)
Sometimes, she mistakes this for me being snooty, and not being accepting of folks who make their living doing something that gets your hands dirty. Of course, she is not fully aware that I come from a family of coal miners and car mechanics. So, that argument holds no water.
Eventually, after 10 years or so, her kids are in their mid-30s, and have moved on from talking about more than video games. They have now lost their jobs, more than once, been evicted from apartments, had cars repossessed, and basically had to deal with life's obstacles. As have a lot of us.
Now that their perspectives have changed, and being able to ask the goofy old guy on how to cope with these problems, we have something else we can relate to.
Sometimes, you have to be the one who changes, in order for the outsider to feel like they are no longer the outsider.
So, you will have to be patient, and let things run their course. Trying to force things, even in a well-meaning manner, might be the wrong approach. It might be a long process. I wish you all the best.