@elmer5678 - first of all, I think it’s amazing that you are being so intentional in your parenting. It takes a lot of work just to do the basics and you are really striving for they “big win” (long term character), instead of just a quick win here.
It sounds like you are on the right track to seek professional support and since you have to wait for a therapist that meets with her - in the meantime you can have someone supporting your decisions!
I’m a licensed counselor who specializes in working with kids. I used to see kids directly but found there was a gap where parents weren’t getting support for moments exactly like this. And there is a lot that can change with her, through some shifts in how you are responding to her behavior. I hear your value of gentle parenting and that is awesome. You clearly do so much to support your kids emotionally and to show how much they mean to you. Also - there are often small tweaks you can make from what may be a bit of overly gentle parenting- to be sure you are parenting with kindness and firmness at the SAME time, to build more emotion-regulation, respect and responsibility (that many parents are missing).
If you’d like a free consult- let’s talk!
Https://calendly.com/sustainableparenting/30-min-free-clarity-call