You just might have to use a "toddler harness" on her... it's for her safety AND yours... a hurt child or pregnant Mom. What if you fall while chasing her out into the driveway, or from the car back into the house? You might just have to use it from your house until you get to the car and visa versa, then take it off. But you have to tell her the purpose of it.
And if she screams, then so be it. That is better than having a child run over by a car or you getting injured.... and pregnant.
They have the toddler harnesses on Amazon.com it's real cute, with animal motifs... I got one for my son. For some kids, it's Very necessary...it is NOT mean. It is for safety.
Or, there are driveway safety gates I believe... just try research it online.
Kids this age do NOT have impulse control... so even if you "lecture" her about it or make examples for her, it will STILL be a safety hazard and she WILL do it again. Keep this in mind. They are not yet mature enough, emotionally or impulse wise, to just "stop" at will, even if a car is oncoming. AND, you cannot just assume that it will stop... children are VERY impulsive, quick, fast, and can disappear before our eyes...
Best to be safe, than sorry, and use ANY safety devices you can. Do not second guess a toddlers reflexes and "self-control"...they are not old enough yet.
Good luck
Susan