Maybe your therapist isn’t as well versed on how trauma typically comes out, especially the first time someone tells their story?
If this is the first time you’ve ever shared about this particular traumatic event, it’s normal that your recounting of it would be very dry, emotionless, clinical, even sounding like you’re reading a textbook. That’s how it was the first time I shared my trauma experiences in therapy. It’s been lots of other people’s experiences too.
Processing through the traumatic experiences in therapy as well as other work done in therapy sessions eventually helps you connect emotions to the experience and it also becomes a more normal memory, and subsequent recountings would reflect that.
Your therapist may have simply been noticing this with you. She may have been trying to normalize it for you, and you may have taken it as criticism or something.
Or your therapist may have honestly been surprised, especially if she hasn’t worked a lot with trauma.
If you and she have a good rapport and work well together, then do tell her how her response landed with you so you can have a conversation about that. Working through stuff like that is part of the work of therapy too.
If she responds defensively to you bringing this up, then that’s a red flag to be aware of. A good therapist will welcome what you bring and explore your feelings with you, even if your uncomfortable feelings were provoked by something she did.