If you have issues with dissociation, your T and you should first work enough on helping you not dissociate and her to notice when you do so she can help grounding you. It's not something you just need willpower for. Tell your T you do not know how to ground yourself well enough and that you first need help with that.

As for the nurse thing, I think it is very important that everyone on your mental health team works together. Doing multiple approaches at the same time can be difficult for people. It's not that hard to work as a team, they just need a few phone calls.

I would again tell your therapist (not the nurse, because she does not currently work in mental health, I think your T has the authority here) that your nurse would also like to work on trauma related things, and that you'd like them to discuss, even if just to exchange opinions and so on.