Yes, zoning out is most definitely a type of dissociation. I have experienced the same thing in similar situations as well.
Your t really should be mindful of these signs of dissociation and what is triggering it. It means that you are protecting yourself and not ready for the emotional content or memories that are being activated. It is also completely understandable that this happened during body/breathing work. We hold trauma memories in the body. It is best to go slowly in therapy--it's not very helpful at all if it destabilizes you or causes you anxiety and depression. Isn't therapy supposed to improve functionality and quality of life?
This is a lesson I learned from my current therapist. I am doing so much better than with the last one. My last t moved so fast and worked with some super traumatic material right away. The result was that I became unable to manage my life and my symptoms, I started drinking... It was bad. But I just went with it because I didn't know better.
I encourage you to find a way to communicate with your therapist about your dissociative symptoms and even inquire what training she has received in working with dissociative disorders. It looks like she is not recognizing what is happening to you and not responding.