This is exactly how I see this situation too. OP’s experience reminds me of how a friend I was close to at one point and had an almost 20 year friendship was. Some self-reflection really helped me realise I needed to drop the rope with my friend, who I’ll call Cindy.
My advice to the OP is think back to past experiences with a critical eye and see if you can spot patterns of behaviour. YANBU OP. I think you might have been too forgiving in the past.
In my case Cindy had always been flighty. I’d known her since primary school, we became close friends when we were doing A levels. Cindy applied to do the same course as me at university, which pretty much became an extension of school.
After university Cindy would make plans to catch up when she was coming home for particular weekends but closer to the time would vanish. I’d struggle to get hold of her, much in the same way the OP described with her friend.
At the time I had to work some weekends and so planning to do things on a day/night off only for plans to fall through was aggravating and unfair. Cindy also had a habit of letting the cat out the bag unintentionally and I realised on some occasions had ditched plans to meet up with me to do something else but had lied to me about why she suddenly couldn’t meet up. I was too polite back then and wouldn’t say anything.The times I had confronted her about things previously we’d ended up having huge fights. I therefore didn’t say when she annoyed me to keep the peace a lot of the time. I realise now how stupid that was.
It got to a point where it felt like I was doing all the initiating contact too, so that was a big factor in why I dropped the rope, to see how things developed. I’d also begun to feel Cindy was in a habit of getting in contact with me only when she had nothing better to do when she came home. The last time we made plans Cindy had asked me the evening before were we still on. I’d replied yes and she replied, “great, see you tomorrow.” On the day I arrived but Cindy was a no show. Couldn’t get hold of her. She eventually replied after I’d been hanging around and window shopping to say, “sorry, I met up with [another friend] and lost track of time.” I uncharacteristically replied, “ok, whatever.”
I then did my self-reflection exercise and realised this was the same character trait she’d shown since primary school. I’d changed primary school in Year 4 and initially Cindy wanted to spend time with me, talk to me etc because I was this new person - almost the equivalent of a shiny new object. However, the novelty wore off and Cindy pretty much dropped me. She‘d been really pally with another person and that friendship seemed to be a friendship for life… until Cindy dropped that person during A levels, which was when I seemed to become Cindy’s best mate.
I haven’t spoken to Cindy for 10 years. I was the last person to send a message and it was a friendly one too.