I agree 100%. They can REALLY drag their heels. There's some good advice here.
Shane: don't beat yourself up about it. You made a mistake, we all do from time to time.... so did the guy in the Navara by not leaving a sufficient stopping distance. Just register the accident with the insurance company, keep it civil, and it should turn out OK. Get your GF to see a doctor about the whiplash. I'd suggest she looks up how to ease mild whiplash on the internet, to lessen any lasting muscle damage. I think the advice is a warm towel around the neck, but I wouldn't take my word for it.
Whiplash is a nasty condition. These "where there's blame, there's a claim" people make me sick when they try to prod people into filing a claim, but there's a big difference between what some of those people are trying to claim back, and claiming just what you're entitled to.