I think it's perfectly normal for friendships to fade in and out.
I've currently got a friendship on the fade. An older lady I became friendly with through a shared interest. We used to meet up about every 6 weeks, but in the last year or so it's been less frequent. I last saw her at the very beginning of August to give an idea. We've also got nothing in the diary coming up, and tend to book things for 3-4 weeks time...
I like her, but she's an odd character who seems to live her entire life in a state of fretful worry over complete non-events. Things I wouldn't even blink at cause her weeks of extreme anxiety. I'm not that way AT ALL, so find it rather wearing to hear about these non-issues hyped up to such extremes. But it almost feels like she enjoys it... She tells me about them with such... relish.
I text her earlier in the week about looking at some menus for our annual Christmas lunch, and got very short shrift. "I can't possibly think about that. I've been in constant agony all week with a bad back." I've learnt from experience that her idea of "constant agony" is most other peoples idea of "I had to take a few paracetamol." I just replied something bland like, "Oh dear! Get well soon." I'm sorry, but if you were genuinely in "constant agony", you'd be in hospital. And so I planted the ball very firmly back in her court.
I'll be pleased to hear from her when she does next reach out. But I've reached the point personally where I'm not going to chase.