How far out do you schedule? 24, 48, 72 hour?
What is the proper time that Provider should respond and confirm an appointment?

was confirmed so therefore she has nothing to blacklist you for.  It sounds like she left you in limbo in case a "better" appointment came through, which she can do but she should have informed you that she would have to get back to you.  

If she blacklists you, then you can let her know you'll write a negative review about her.  Its a two way street.  

...if he didn't actually see her he can't do that (write a bad fake review).
TBH I would probably risk the blacklist if in his position and if brought up i'd explain the situation to the lady who asked. These days because of situations like this is why smart providers should take blacklists they read/see with a grain of salt.  You guys do have backchannel (like the RO board as well)....use it.

If the provider blacklisted him, then that means in her mind there was a cancelled appointment.  He can respond to her 'review' for clarification for everyone.

No matter how far ahead I book, I always confirm 24 hours or less before the meeting. I think that's pretty much standard. I've known providers who won't even schedule a meeting more than a couple days ahead of time. In this business a lot can happen, and change, in 24 hours.

I don't want to flood a Provider with emails. If I hadn't heard from her 24 hours prior I felt there was no interest on her part. If I sent email after email I believe it would seem like I am harassing her and would push her away from accepting an appointment with me.

but sometimes when I'm traveling it's a little more difficult. I'm currently in Boston and I had trouble confirming dates on my way here because the wifi on the train was down. So instead I spent my time way into the evening attempting to confirm appointments. For tours I tend to confirm a week in advance and then again the day before with meeting information, but once I do the week before confirmation I assume my dates know I am committed and just write the day before with info.

a simple 'Did you get this?  I haven't gotten an answer unless my spam filter ate it.' and no one would think of that as pressing.

We have corresponded since I posted here. She said there was confusion in her email when I responded to her. She isn't going to Blacklist me. She has offered me a discount on a session on this or her next tour to the area. I appreciate she admitted her mistake. I have a multi-hour appointment schedule for Thursday and we will take things from there.

One of the lessons I have learned is to try to communicate with the lady on multiple forums to schedule an appointment - her website, email, as well as P411 and PM here. Usually just try 2 of these, but it increases the chance that she will actually see the appointment request in a timely fashion.
Unfortunately, not all ladies are diligent about responding quickly to appointment requests. Like they have real lives of their own!! LOL