I have a standing appointment and T tells me when she knows she will be away. I have also learned to think ahead; just last week I asked if she was taking any time at Christmas. She doesn't have plans now, "but that could change". I like that she put it that way, leaving options for herself. It is like how I learned it is okay to not immediately commit and can say (to anyone) "let me think about that and get back to you". So it was that last comment in session before the door was opened and it was something good to observe and experience.
She also thinks ahead and offers me another time when there is a holiday on Monday, my usual day.
Other times she has had a cancellation and called to see if I want to come earlier, or keep my scheduled time, either way is fine.
And she has adjusted her schedule for me, and once met with me on her day off. She was already coming in for another person, but she took extra time for me. She has stayed late for me when I ask for an emergency appointment, too.
I guess I'm trying to say that I try to look at the whole big picture, if I can, when a scheduling issue comes up and bothers me.
On the other hand, my previous T offered Friday appointments, but then cancelled every Friday for a month, after a few Friday cancellations the month before. I decided that wasn't going to work for me.
I hope you can talk to your T about your feelings that come up when she has to move or cancel an appointment. She needs to hear your thoughts about this.