I just came across this blog about the 3 kinds of friendships according to Greek philosopher Aristotle, as interpreted by an academic.

-utility based
-pleasure based
-character based

The crux of the article's message is that friendship buffers us from loneliness, and when we aren't clear with each other about our mutual roles, then that is where conflict happens. I think this is why I continue to have difficulties with friends - I don't clarify which of the 3 based types of friendship I'm in with this other person (either clarify to myself or with the other person, so that I am clear).

The Great Conversation: Aristotle on Friendship - Associate's Mind

The former friend was a utility based friend (writing being the connection). The FL friend (I assumed and was incorrect as it now turns out based on her reaction to my postponed trip), is also utility based, whereas I thought our friendship was character based. I think moving forward, I will try to place people in each of these 3 categories so that I stop being disappointed, and keep my expectations low to avoid being taken advantage of or hurt emotionally. Easier said than done. But awareness/hindsight has to count for something. Or maybe I just am not built for friendships. Who knows.