Firstly, there’s nothing I will say that hasn’t been said.
My emotional flare ups have been THE HARDEST symptom to manage in my 20 year diagnosis. Medication is essential for me, but it is not the only thing. I need a combination of meds, the right therapist, and the right LIFESTYLE to keep my emotional responses under control.
Even with a great therapist, psychiatrist, and meds, I still have problems right now because everything else in my life is stressful (too much desk time at work, buying a house, etc).
I try to be aware of this and tell my partner when I need to be alone or need a break from a conversation because I feel myself getting heated. Try and come up with a signal to pause a conversation or argument that EITHER of you can use as a “time out” signal to walk away and regroup. Have the other person write down their talking points so that you can finish the conversation at a better time.
When she is getting explosive she should make sure she has: eaten recently (quality protein especially), slept enough, gone outside for a short walk, etc and if not, try to find a way to encourage her to do that. I know if she’s already in exploding mode it will be hard and she will probably feel offended by your suggestions so try to talk them out when you guys aren’t in a heated moment and plan ahead.
If your wife is in therapy and on meds already, you two should evaluate their efficacy together and also look at lifestyle things that may be increasing her ADHD overwhelm and prohibiting her from better examining and managing her outbursts.
Best of luck to both of you. She probably feels a ton of guilt and anger towards herself for behaving this way, so do remember her anger is likely coming from somewhere internal.