No win no fee usually applies only to that companies fees - not the costs of medical reports or any third party costs such as court costs.
I would not touch one of those companies with a very long barge pole. If she genuinely has a case, why not use a local solicitor who specialises in personal injury? If she wins, the other side will have to pay all the costs.
My feeling is the company does not believe she has a 100% chance of winning and want to back out. They make their money from wining cases so aren't interested if there is a chance of losing.