Does she ever provide a reason, not that I guess it matters.
You are doing better than me though, messages on AW go unread, WA and texts also and phone rings out whenever I have tried to contact, almost as if I am blacklisted! 
When she’s had to cancel she’s just said cannot make it somethings up etc, but I don’t worry about that as its not last minute. Couple of examples of the negative drivers…
Had meet set for a certain day / time. Couldn’t get in touch on day of meet then later in eve she says she lost phone in the park and now available for xx day / times. Arrange for another time and as I’m heading out…radio silence. Basically, I was probably bumped for some regs etc…the usual.
Another time we’re set for a time and then she reschedules at last minute saying she’s coming back from her sisters…quite clearly another meeting has extended…
While she’s one of the best service wise in London, it’s these things that prevent me listing her as #1.
I can imagine that when / if you finally do meet her, it’ll likely be positive. The question I would advise is how much do you want to see her and can you be bothered with the unreliability. I can to some extent….but will always have a plan B right up until the point of entering the door.