Sorry to hear about this Ryan it looked mint at the meet, silly old bint.
I wouldn't worry about the exhaust not been declared, 1. they probably won't notice it 2. it will be going through her insurance.
Her insurance will be paying for the repair so they won't even get to see your insurance policy.
A mate of mine was stationary on a 30mph road waiting to turn right as there was lots of traffic coming the other way. An OAP went straight up the back of him at 40mph+ in a huge peugeot, my mate was in a Saxo 1.1. The old b*****d didn't even brake. The Saxo had undeclared lexus lights (lol) and an induction kit. The claim went through and he got a very good price for the car, he also got £2k compo for whiplash.
The same lad wrote of his Zetec S about 2 months ago, no other car involved was going to quick and swerved to avoid a cat and put the car up a kerb and into a tree, shattering one of the alloys. That was lowered 40mm+ and was part of the reason for the damage to the underside of the car, gearbox etc. The garage that recovered it noticed the brightly coloured springs but the insurance accessor didn't, claim went through fine.