Yiikes. I know I wouldn't do well with that therapist. Trust is so very important, and I can see why you just don't trust her.
I think, when dealing with complex trauma, a therapist who is well-trained and up-to-date with trauma-informed therapy is absolutely crucial. From all you have said about your T over the months I honestly don't think she is qualified to help you, C and the others through this.
I am very picky about my Ts and I have been through a few that were not up to the tasks I need them for. The difference in the amount of progress you can make with a properly trained T vs one who isn't is ENORMOUS. It's the difference between trust, safety, engagement, and healing vs distrust, game playing, ruptures and being stuck. A properly qualified and experienced therapist is a game changer.
I hope you and C can find a way to change the game.

Hello, I want to add that our therapist is awesome. She calls us by our own names and respects everyone in the system. She helps us to respect and appreciate everyone too, even the ones who are really different to us and want really different things. I hope you can find a good T who can really help you all too.