I was going to suggest a couple of things that you should have done but hindsight is great and obviously you don't want to hear it.
I would get your statement to your insurance company and insist they contest it. The damage certainly looks it was caused by reversing so this is the line your insurance company should take.
BTW – What is the damage to her car.
Also, it sounds like she knew exactly what she was doing i.e. leaving the scene knowing that her car would be difficult to trace and that you wouldn't get any witnesses!