If true I'd guess a random drunk accident that was covered up, but who knows!
True, but with the blackmail plot being wrapped up earlier than intended plot points that were originally supposed to be spread over several updates will probably have to be thrown together quickly. We know the plan with John isn't going to work so the way Ethan gets stopped must be something else. Linking him to Rachel's murder is the obvious one, but the car crash is another possibility...
In my opinion the car crash is kinda "too outside" his thing, he's a bully, he can get aggressive with women and people who are weaker than him, he's obssessed with a certain blond lady, he works with escorts... this is why the Rachel case makes sense for him.
A hit and run on someone(Dani) that as far as we know holds no interest to him is a bit... random... for my taste.
Unless... Dani never got hit by a car, something else happened to her and they used "she got hit by a car" as an excuse for her not to attend school for a while and rest, get over what actually happened.
She's also fairly quiet and reserved...
She doesn't have any visible scars and is in amazing physical condition

for someone who got seriously injured by a car.
Santiago might know something about this... since(we suspect) he was married to her sister Gabi.