I hate when I have to cancel appointments. And I HATE when I'm late, though I've only had that happen once or twice, and only be about 5 minutes... due to traffic and poor planning.
I have one client that shows up at 9am for her 9:30 appointments, we have an understanding that she will just sit and wait until I am ready. Usually I am not there until 9:15am, but there is a nice park bench in the lobby just outside my suite door... but I am rambling.
I have a $25 cancellation policy. If you cancel less than 24 hours in advance, I may charge for that at my discretion. (I usually don't if it is a longstanding client, or if there is illness or emergency... I don't want what they have, LOL! and would rather they cancel than infect me.) If I cancel with less than 24 hours notice, I generally will give the client the $25 "cancellation fee" off their next visit. I did not do this on that day I had my car accident, because all of my next day clients were regulars, and I was able to reach all of them the night before their appointment. (Plus I would have been out $175. Ouch.) Other than that, if I expect them to keep their schedule, they should be able to expect me to do the same thing.
On the other hand, one time I did cancel someone at the last minute who was a new client. I had a gut feeling it was not legit, but I scheduled him anyways. The next morning I had a migraine... one I would have worked through with a regular, (meds and all...) but it was a good excuse to go with my gut and cancel. I did not offer to reschedule, and I never heard from him again. Is that fair? Probably not. Was he legit? Yeah, probably (but trust your gut...) Do I feel bad? Ha! No.
Look, my opinion is that if you find a therapist that is a good technique for you, but you know they are flaky on time and schedule, if you choose to stay you lose the right to kvetch about it. You KNOW this is possible with every appointment you make. It's your trade-off.
Ace, you commented that the "problem" can be avoided in the future... DON'T bet on it... she's shown that she is incapable of adhering to the appointment as scheduled, either by being late, cancelling or running long. It WILL most definitely happen again, I'm betting most of the time too. She's not going to reform just for you, it's how she operates.