I absolutely think you have the right to ask her! It may be MORE important because it has happened 3 times in 9 months. Seriously.

I used to see my T on Saturday's, and I quickly figured out that she runs about 10-15 minutes late. It freaked me out at first, as I had never experienced it before, but she was quite consistent in her late-ness, so I eventually adapted.

We ended up having to move sessions to a different day after work, so now she waits until I can get there. A few months ago, she mentioned something about her late-ness, and how a potential client had fired her because of it. I said "Wellll...." and told her how i was freaked out for quite some time, but never would have told her.

She was enlightened. She said her supervisor told her that her clients probably wouldn't say something if it bothered her, and that opened it up to me to tell her how I had felt.

That entirely too long story is to tell you that, if it bothers you (and it should!), you should say something. Even if it was the 10th session and she had cancelled once or twice, you have every right to tell her it upset you and why.

I think my T was a little surprised that I was freaked out over her lateness, and all the thoughts that followed it (what if she forgot me? maybe i have the wrong day?! i am not important!....etc), but she took it in stride and it hasn't been an issue since.