It is misleading to say the police federation is supporting her claims, they have referred her claim to solicitors.
As with most Unions the Federation offers as part of its membership legal services for those who suffer injury at work. She has taken advantage of those services to bring, what on the information provided, a ridiculous claim for injury. It is however the solicitors that will have advised her not the federation.
Hopefully the court will see this for what it is and throw it out with costs against her.
After all this has been settled (hopefully in the garage owners favour, but you can't be sure given some of the perverse decisions that come out of courts these days) I would be really interested to find out what the federation actually advised her to do.