I am a law school graduate. What I offer is mere information, not to be construed as forming an attorney client relationship.
FIght the ticket, because officer must have seen it happen, otherwise, it would be invalid.
Your friend should argue no police witness to traffic infraction is a lesser kind of criminal offense, like a misdemeanor. So, if officer needs to see a misdemeanor happen in order to arrest, shouldn't same be held to give ticket for traffic infraction.
Of course she was following closely, maybe?
What if the person in front suddenly stopped for no reason? Shifted out of gear?
Was there a thorough investigation done by insurance to target her as the wrongdoer?
Get it? Sort of prove your innocence mentality when it should be innocent until PROVEN guilty.
If you wanna get technical, what is the municipality your friend is in?
Check the municipal code to see laws covering police giving traffic citations after an accident or in general: when, where, how, why