Your screwed Canto, any rear end hit regardless the front cars actions becomes your fault. There is no "free" fix, your insurance rates will be going up probably 50%. She will be collecting money for neck injury, head injury anything she decides to cry about. I had this done to me when I was young by a drunk who pulled over on the shoulder and then came into my lane quick as I was going past. I paid the insurance accident surcharge for over 3 years. My daughter had the same thing downtown at less than 30 mph, two cars infront of her stopped dead fast, second car slamed the first, my daughter slamed the second car, which obviously stopped dead SUDDENLY in front of her... quess what ? My daughters fault. Drive way out in front of you in the future, there can never be too much space between you and the car in front of you.
Im not saying this is the case in your situation but there are people that work out these rear end schemes to hit the insurance lottery and it seems pecular she had a "3rd party" witness lined right up. Perhaps the Benz payments were becoming a problem....
Any accident get right out with those expensive camera phones most everyone has today and get pictures immeadiately, dont ask some idjut that just fucked you if they are OK, fuck that, get snapping photos. In this case photos that there were no cars infront of her, the idjut sitting beside her, presumable that there were no skid marks by her but some from your car... of course anti lock brakes will fuck you everytime now, they also wont get the job done in a panick stop either and let you down everytime.