First of all, it's great that you are taking to her about difficult subjects. What you are experiencing afterwards is incredibly common.
On one hand, therapy isn't just supposed to stay in the therapy room. It is designed to be something that impacts us throughout the week.
On the other hand, anxious ruminating can be really counter productive...
I'd suggest asking your therapist about ways to "contain" the work, and how to leave the thoughts and anxiety in the room.
Sometimes, when I get stuck ruminating about therapy after the session is over, I'll journal about it, and make a note of what I was anxious about as something to talk about in therapy the next week. If I'm super anxious, I'll actually skip the journaling and just make a one sentence note to talk to the therapist about whatever's on my mind. I'll physically write it down, in just a few brief words, and then purposefully put it away. I'll put it in a drawer or close out the file on my screen. Then as it comes to mind later on, as it almost always does, I'll remind myself I've put that away for later. I'll remind myself of this as many times as it comes back up, and eventually my brain will get the message. One common CBT technique is to picture a stop sign when stuck. I picture a sign that says "later" - because it still gives myself permission to deal with it.
If it really gets to me, then I'll schedule a limited time to think about it and then at the end of that time, I'll go do something else that takes as much of my attention as possible. Anything safe that requires me to focus on this moment now. Stuff like cooking a really complicated dish or shooting hoops (which I'm terrible at.) This kind of active mindfulness, to this moment now, can help pull me out of the loop.
Finding physical ways to downgrade the anxiety can help. Excerise, doing deep breathing, engaging in fun healthy distractions, etc.
Addressing post symptom spikes is a common part of therapy, so be sure to talk to your therapist about this.
