This sounds as good a case for potential insurance fraud as any that I have ever seen.
Easy potential racket if you think about it. Take a picture of your "pride and joy" (don't underestimate the sorts of vehicles fraudsters will use, some of them crash brand new cars via slam-on as the payouts and appearances are better), wait until nice honest driver has gone, get a mate in to do the damage in some knackered old thing, if actually clever then use a similar colour car, claim nice honest driver was to blame and it's your word against theirs.
My suggestion would be to hint to your insurer that you think this may be a fraudulent claim, depending on who your insurer is some currently have a zero tolerance policy on the matter and will refer and fight every single case even if it costs them money. Some unfortunately still go down the "it will be cheaper to pay out the fraudulent claim" route, however if they have admitted it's fraud but they are paying it anyway then it no longer becomes your aunt's problem.
As others have said, it us up to them to prove she did it, you have physical evidence she did not and are quite happy for it to be tested. Tell em where to go.