I'm sorry about what happen. I certainly hope that you press charges against her, regardless of how badly she will suffer from DUI.
1st time DUI isn't likely to have her serve any jail time. Its people who drink and drive like this who kill other people on the road.
Think about it, if that person has the audacity to "hit and run" and attempt to steal your car(attempted grand larceny). That person probably would drive away if she hit a pedestrian.
I would file civil charges as well. Make her really pay.
If she can afford a Merc, she can afford a decent lawyer that will probably get her off with a restricted license.
I would make it worth while to make her really learn her lesson.
Just my 2 cents.