what she needs to do is to go to the hospital, so there's proof taht it is food poisoning and she should have done this immediately.
I work in a 'resturant' and beleive me, Brits have NO problem complaining about ANYTHING. A couple of times we've had people say they've had food poisoning from us-once they looked fine, the second time the hospital confirmed that it was a virus.
You are actually alot more likely to get food poisoning at home.