Coaches for tweens

My 11-year-old daughter has a problem with violent, angry outbursts (kicking, punching and even biting on occasion). She is very bright (gifted and talented program at school), a twin and one of 5 children ages 7-11. There is a lot of fighting between siblings, but she is the one who really becomes violent. Over the past couple of years it has just gotten worse and worse. Often there is no visible build-up to diffuse – she goes from normal to determined to inflict pain, seemingly in an instant. Last summer she actually kicked the passenger window out of the van while we were driving, and then recently she got a 2-day suspension for hitting her sister at school right in front of a teacher and then locking herself in the bathroom stall.
She learned some coping mechanisms in a 1-session stint with a play therapist that all the kids attended last summer, but she is usually resistant to using them. In the moment she feels justified in her feelings and behavior.

Since listening to the podcast and joining Scholars in April, I have started using different language with all the kids (thoughts vs. feelings, actions etc.) and really tried to model better responses to anger myself. She is in middle school and now that this behavior has leached out of the safety of our own home, I feel it’s time for some outside help (for her and/or us). My husband is very resistant to counseling, but seems to be open to coaching. Is that even a possibility for someone her age? Do you have any coaches or advice you would recommend?