I didn't know you were also a T... that does muddy the waters a bit doesn't it? Ethically, there are responsibilities you have that a regular client doesn't.

Does your T allow email between sessions? I wonder if maybe approaching her from the mindset of another T with concerns rather than her client might help you a bit. Compartmentalize it, I guess, and email may be easier than face to face, cuz you could work out the wording to your satisfaction before sending it. Instead of your hurt and your disappointment, approach it that you need to be sure she is not "breaking the rules" (I can't think of another way to phrase that...).

Maybe, express that as a T, you are required by XYZ licensing agency to report any possible ethical violations you are aware of, and you need to know what is going on, why she is missing so many appointments, and if there is a logical, acceptable explanation for it.

Taking out the fact that you are also her client, there are other clients involved, and if you were simply a colleague witnessing this behavior, I imagine it wouldn't be so difficult. Hence the muddy waters...