I had a friend like this.
In the end I allowed the friendship to fizzle out.
Although it kinda had because she always flaked and things were on her terms and she'd found another new BF for a period of time. From for this but our time spent together was good so I lived my life and enjoyed time with her when I could.
I agree with you about feeling valued.
When we were closer as our kids are same age and met a lot to do things for them I took back control by making our arrangements less dependent on her attendance and less formal.
For example (text)
Me: taking to ds to beach at x around 10am Wednesday. Welcome to join if you want
Her: yeah that'll be good see you 10. Shall we meet at x spot.
Me: we are going to be at y doing a,b,c if you turn up
Her: ok.
On the day
Her: (10.01am) sorry running late. Need to go to ship to get picnic, new clothes for this activity as kids have none (for some reason she did this constantly so I've no idea what happened to clothes they worn to beach week before
). "
Me: no worries
Her: are you there yet
Me: yes
Her: are you doing activity
Me: yes
Her: oh my kids will be disappointed they were looking diehard to doing it
Me: well when you arrive you can do it with them
These sort of exchanges and change of control made me feel less let down and she didn't like the fact I didn't care she hadn't arrived. Previously we always arranged to go places travelling together which meant I was waiting around or trailing around shops with her for hours before we got somewhere.
Unsurprisingly when I stopped being her personal lapdog that's when she started finding other "best friends" to hang around with.
Basically other lapdogs 