How much responsibility is on the therapist to help a client when they're dissociating?

For context, I have past trauma from a therapist I saw several years ago. I'm working through this trauma with a therapist trained in trauma who has great boundaries. Due to the specific source of my trauma, it's easy for me to dissociate in session. I've talked with her before about it and told her signs she can look for to tell when I'm dissociating and what she can do to bring me back (speak gently to me, remind me that I'm with her and not my ex-therapist, make a joke, etc). I've told her that sitting in silence, sounding frustrated, or pressuring me to speak will make it worse. I also have a history with SI and I don't currently have a support system (no partner, no family, and I recently moved to a new city where I don't know anyone). So she knows that ending a session with me in a dissociative state without grounding me can be really unsafe.

In our most recent session, I dissociated really badly after she asked me a question and I went completely silent. She sat there in silence I think for maybe a good 5 minutes or so before she finally said something like "you don't have any response to that?" and after another few minutes, "anything?" She said something else, I don't remember what, which made me start crying and talking to her as if she were my ex-therapist (which happens a lot). She said something like "I don't know what you mean by that" which frustrated me even more because clearly none of it made sense, I was not in the present moment, I was stuck in the past thinking I was back with my ex-therapist and needed help being pulled out of it. We were past time and she mentioned that I'd been dissociating for about 10 minutes and asked how she could help me. I got angry with her and said "you didn't help me, you did nothing for 10 minutes" and she said "I'm asking you now if there's anything I can do to help you" and I said "no, I'll handle it on my own like always." I know she didn't feel great letting me hang up but also she wasn't getting anywhere with me and we were over time.

I feel really upset because I'd told her specifically how to help me when I dissociated and she didn't do it. Even if she didn't do what I asked, surely trauma therapists are trained to ground their clients somehow instead of just sitting there for 10 minutes barely saying anything? She's a really great therapist and I trusted her a lot, I don't think she has any malicious intentions, but I'm interested to know exactly what she thought would be beneficial about just sitting there in silence for that long and not really doing anything? I guess I'm just curious if I'm being too sensitive and dependent on her expecting her to help me and I should've just forced myself to snap out of it, or if she should've done more? Thanks in advance.