<human>: Can you summarize the given text in a few sentences?

Here's the backstory:

My girlfriend, her sister, and my cousin were all waiting for me at my doorstep while I was quickly getting changed to go out clubbing. 
 
While I was changing, they went outside to start rearranging some of the cars in my driveway, because my mothers car was blocked in by other cars. My cousins needed to move his car first, but to save some time he asked the girls of they could move my moms car out. He asked my girlfriend first to which she replied she didn't want to, and next she asked her sister who was fine with doing the job.

After that things start to turn for the worst. As she started to back the car up she floored the gas (I have no clue why) and she t-boned a car that was parked on the other side of my street. 

At this time i came outside, and Immediately she was begging for us to flee the scene, and after her initial claims to pay for everything, I figured we could deal with it when we get back home. 

A couple hours later we get back and the car she hit wasn't there anymore. Still thinking she was going to pay for everything, I drop her home and decide to find out who's car it was in the morning.

Now this morning, she switching up her stance saying my cousin needs to pay for half of the damages since he asked her to move the car. While I agree that he shouldn't of done that, I think it's her responsibility because she could have refused at anytime, and it's pure negligence that she didn't notice the car directly behind her. 

I want to find out who's car she hit ( I see it on the street often) and report the hit and run before anything gets worse. I'm just not sure exactly where to go from here. 

The bumper costs $1000 to replace and install, btw. And she is In her mod 20's if that makes a difference
<bot>: my cousin asks my girlfriends friend to move my moms car out of my driveway while he moves his as well. She floors the gas and t-bones it, and refuses to pay 100% for either cars damages