Is this a case of AoG playing the "stiff upper lip" card? :) Those with right wing tendencies are made of sterner stuff than them wishy washy long-haired, unwashed liberal-lefties?
The BNP are a legal political party - they have a democratic right to protest policies they disagree with, subject to the law of the land over the timing and location of the protests.
Similarly, because we live in a democratic society, those who find BNP policy repugnant have a democratic right to arrange a protest.
As for this woman - she may have called out "you have broken my leg" simply because it felt as if it had been broken, without necessarily knowing it was. Myself, I would have liked to have seen some kind of comment from the medical professionals treating her - I do wonder a little whether she is milking or exaggerating what happened - but of course her medical notes and treatment would be private....
And yes, of course she has a right to make a complaint. We employ a police service, whose remit is essentially to protect and serve, not uniformed hooligans willing to batter anyone in their way with a baton like that PC in the G20 protest, or kick out at protesters as appears to be the case here...