A Vero Beach lawmaker said Wednesday she will again file a bill to repeal Florida’s no-fault car insurance system, but with key differences compared with a Senate bill introduced days ago, setting the stage for the biggest potential change in motorist coverage in almost 50 years. At stake: whether Florida drivers can save up to $1 billion a year by ending the no-fault system. It imposes what many drivers see as a fraud-riddled, costly and unnecessary duplication of their health insurance, while allowing at-fault drivers to escape responsibility for harm they cause.