It sounded like she was with the group of protesters who didn't have a valid permit or their permit had expired (I recalled it was the Anti War Committee). Leah Lane was standing on the street alone, singing "All you need is love." The video footage showed that she wasn't resisting the arrest, but she wasn't obeying the police order to leave the street either. So, I don't really see why the police couldn't use force to arrest her and remove her. FOX 9 repeatedly showed the footage of her getting knocked by the police's bikes.
I bet Leah Lane is heralded as a hero by the anti-war protesters. Or she is regarded as a pacifist by FOX 9 Trish Van Pilsum. But I have a hard time to have any sympathy for her. If I did what she did or if anyone else did what she did, it would be the same consequence. Not obeying a police order will land you in jail.