My sister also has ADHD, and some level of misophonia.
I recently encouraged her to buy some adjustable Loop earplugs: https://us.loopearplugs.com/products/switch
She can dial in the sound reduction level she wants, helps her at work, helps her at concerts, helps her when hanging out with friends in a noisy restaurant… etc.
I might not recommend them for driving as you probably need to hear what’s going on around you, but for many tasks they can be amazing.
Please buy a better carrying case for them though. Hers opened up and she lost one of the plugs, and now needs to buy a new set.
If she really needs QUIET she’ll put on some over-the-ear industrial muffs, but the plugs are great for just everyday usage.