I understand your emphasis on not crossing a line that gives the stormtroopers free rein to wallop you, but in light of what's been going on at the Portland protest (and at other protests around the country), there's no reason to assume that they wouldn't have assaulted her regardless. If these fed goons were playing by normal rules their agencies and very identities wouldn't be so opaque.
She instigated it. She was being purposely aggravating and got too close and thats what happens.
What would happen if you did that to a Police Officer over here? You'd get a warning, then arrested - that was no different, they turned round, she kept doing it and they bit.
Also, there's plenty of reason to assume they wouldn't have 'assaulted' her anyway (they didn't, they detained her) as it didn't happen.