What to do when an old friendship becomes difficult

That explains it then ?I didn’t look at that threa because I assumed it was a family NC type of thing

This happened to me in a slightly different way. A friend of very long standing and who visited us several times suddenly became unavailable when we were due to stay overnight with her. All phone numbers and e-mail addresses somehow were 'lost' until the date of the visit had passed. I was quite hurt by this and the friend has established contact again without any real explanation. I cannot feel the same friendship any more and my replies are brief. My husband thinks I should forgive and forget but I can't.
I think sometimes these things run their course and its time to let go but its quite sad.

Friendship is a two way street, doesn’t work if only one of you is making an effort

Her husband sounds very overbearing, perhaps she is afraid to spend money on enjoyment. I would try to see her on her own and not treat her as a package with her husband. She could become isolated because no one enjoys his company.