Pete, i can answer your first two. She was protesting against the G20 summit and, following the previous days violence, the protestors were ensuring that they distanced themselves from the handfull of morons who had caused trouble. They did this in a similar vein to the 60s anti vietnam protesters with bubbles rather than flowers.I think you have to ask the following questions:-
a) Why was she there in the first place?
b) Why did she have in her possession bubble making articles?
c) Why was she blowing bubbles toward the policemen ?
These are not arbitrary or accidental actions, they are quite deliberate and therefore need explaining ...
As for why she chose to blow bubbles near the cops I can only summise, from the reactions of the activist and the female cop, that she didn't think a 6'+ cop would react so agressively.