You’re correct, death is not the answer here, death lets her off way too easy. Her punishment should be something more along the lines of losing a finger in a car door or something and then having the scars kind of look like your initials so that every time she experiences fantom pain she can’t help but remember what she did.

Also, an enhanced sense of justice is often part of ADHD.

For us older folk, and unfortunately, also for some younger folk that grew up in more “conservative” small towns, borrowing and fancy math trickery was the work of the devil.
We were required to memorize the addition tables as well as the multiplication tables. And even then, addition could be done on your fingers and toes so as long as you could add the big numbers like 8 & 7 together faster than the really slow kid could take off his shoes and work it the hard way, you were considered proficient at addition.
So ya, there’s a wide swath of America that just sucks at basic math.