Have her do what every motorist should do, but very few are responsible enough to take the time and put in the necessary effort to actually do:
READ THE VEHICLE CODE!
Yeah, I know that was a bit loud, but this isn't beanball folks. Americans are so inept behind the wheel that an average person has even odds of being injured/maimed by a motorist in a lifetime.
Read the vehicle code, multiple times and understand every word. I'm not talking about the pamphlet that they give out at the motor vehicle department. I'm talking about the statutes that govern the use of our public right of ways. For most states, the code, excluding chapters that are only relevant to commercial carriers, is only a couple hundred pages.
Secondly, have her evaluate some simple probabilities. (If no one in your household can do the math, hire someone to teach her.) Look at the odds of injuring someone on any given trip (very low). Now look at how many trips she will take in a decade. Now look at how certain behaviors and conditions change those odds, like eating, talking on a phone, being fatigued, texting, being intoxicated, darkness, driving into the setting/rising sun (have polarized sunglasses in the car) and rain. Now repeat the calculation. I hope she can appreciate how we can engage in acts behind the wheel and get away with them for years before the piper must be paid. He will be paid, and it is better that she understands that going in instead of finding herself exclaiming, "How could I have known?"
Lastly, make sure she always has a plan. If she's traveling down the highway and a front tire blows out, what will she do? If her drive train falls apart, what will she do? If her headlights fail, what will she do? If someone steps out from between those parked cars, what will she do? When someone is tailgating her on a two-lane highway, what will she do? When she is traveling at the speed limit but a curve precludes seeing what is around it, what will she do? All of these things have happened to people I trained, and all of them had no problems at all because they knew what to do before it happened. Like I said, this isn't beanball. Lives are in the balance.
In spite of my screen name, I have a fully endorsed class A license and have trained other class A drivers, as well as more than a few class C motorists.