Consultations are perfectly legal. Any medical professional is allowed to consult with someone in order to better understand the parameters of your case. However what defines a consultation is clearly open for debate. If my therapist decided to consult with a teacher regarding something and just happened to choose, for instance, a teacher at my son's school - and decided to talk about my childhood and reveal all of my deep dark secrets, we would have a considerable issue. If he decided to consult with a lawyer regarding specific legalities about my case I would have much less of a problem.
One of those is professional and one of those is not, so there is clearly room there. But, my therapist frequently consults with other professionals almost constantly. Lawyers, teachers, interpreters, other therapists, doctors, volunteer groups, etc. He doesn't ask for my permission. He knows it is very unlikely I would give it in most circumstances. But he does not lie about it either, so I understand that what I am saying may be revealed anonymously to another party.
A therapist cannot identify you, individually, as their patient. They cannot reveal your therapy notes. They can summarize your case and seek opinions and assistance. Think of television shows where a group of doctors will say "female, 45, caucasian, presents with appendicitis" etc etc. It was only with my permission that my therapist was capable of revealing who I was and my contact information to another person that he was consulting. So there is a very thin line between what is ethical and not ethical.
From what you are suggesting, due to the private nature of the group, it sounds like she revealed exactly who you were without your permission. I don't think that is ethical at all. And, I have absolutely no inability calling it a breach of trust. She was extremely dismissive of what sounds like a very important concern on your part.