If i was you mate i'd have a proper read through you insurance policy.

I was driving my mate girlfriends car once and someone reversed straight into me and took the front bumper off. I thought i was insure through my policy, but when i phoned em they said i weren't as i didn't have a certain option on my policy. Luckily it weren't my fault so didn't matter in the end, but still worth checking it out before you go accepting any responsiblity! Cos let face it if nobody saw, and there's hardly any damage on you mrs car, how's she gonna prove it!