Boundraries in Rants

I have a small business, what most would call a micro-business, and I work by appointment only.
Sometimes, clients find they are in need of my services - quickly - they need relief from pain and such. A specialty of mine.
While I’m really willing to work with people’s schedules, I have finally found that I cannot bend over backwards and inconvenience myself for their last-minute appointment requests.
A couple weeks/months ago, a client, from whom I hadn’t heard in a couple months, contacted me to schedule an appointment. THAT DAY!
I’m sorry, I’m kinda booked. Offered another time the next day or so.
Didn’t hear back.
Couple months previous to that, booked that same client (last minute, of course), and the client ended up being 15 minutes late - due to an accident on the road. Ok…totally get that. And totally empathetic to that.
Yesterday, hear from this client - do you have anything tomorrow? My response, about as quickly as I saw the request, which may have been all of 30 minutes, I have 9:30, 10:45, or 1:00 available.
No response until THIS MORNING! To say that she may be available for 3:00pm (not a time I offered, but whatever)…with a follow-up text saying that today wasn’t going to work and she’ll contact me for an appointment later.
What the actual hell?
I am in the process of trying to set boundaries with her, obviously.