You know she’s smart, and she knows she’s smart. So maybe start there. “I know you’re smart. I know you don’t need a tutor to understand the material. So don’t use this person as a tutor. Just use them to strategize with. By all reports people with ADHD do really well with that, so it’s worth a try. I can see that the frustration of your situation is wearing on you, as is understandable given the situation. But this could actually make a difference for one, so give it a shot.”
Ps I was the same way. In high school it was doodling, in college it was videos or games. I never found a class that fully engaged me. I usually got the concept and immediately got bored because I know they would talk about it for another 5 minutes before moving on.