One woman's harrowing run-in with police: Overreaction or justified force?

A few days before last Xmas, Louise (not her real name) gave a thumbs down signal to a police officer. What followed has lead to her heading to court facing four charges, and has left her seriously traumatised. The Independent Police Conduct Authority are looking into her case but it once again raises the issue of justifiable force vs 'police to peace'. How hard is it for our police officers to get the balance right? Could this happen to any of us?