Trauma therapy, whether its EMDR or another type, will be easier and more successful if you have a really strong relationship with your therapist, one where you feel safe. Right now your relationship sounds weak and distrustful. You seem scared of her, angry at how she is pressuring you and not listening to your needs, and feeling like you have to walk on eggshells so you don't offend her. I think feeling comfortable in your body, as your T suggests, might help you not get retraumatized by EMDR, so yes, it might be important. The body exercise is not a requirement for EMDR, but feeling safe is. For you, the feeling safe may involve being able to do the body exercise. However, it sounds like you aren't ready for the body exercise yet, because your relationship with your T is not strong and safe. So my recommendation would be to work on building the relationship by working on less traumatic and triggering topics, for example, how your week went at work, or something else that is just, well, easier. Through this work, you and your T will get to know each other better and you can start to feel safe enough with her to do this body exercise or the EMDR or work more directly in some other way with your past trauma.

If you are scared to tell her what you need, would you want to look for another therapist if you can't get her to slow down? She does sound kind of harsh/inflexible and perhaps not what you can handle right now?