Firstly, your opinion is pretty disgraceful in general that you have no sympathy for police killed in the line of duty. For any policy the government shouldn't have or enforce there are many that are absolutely crucial and the difference between chaos in the streets and not. The world is not that black and white.
Secondly, she should ABSOLUTELY be charged. It's the head in the sand people that let these situations escalate. It starts with people like her, but if nothing happens to her and all she gets is a bunch of feminists supporting her in 10 years she'll end up on some board at a university able to genuinely effect peoples lives with her horrific beliefs. Similar people who said similar things a decade ago who are now in positions of power are causing major trouble. The way american universities are going is laughable. Guys who get thrown out of university because of proven false accusations of rape because crazy feminists on the board refuse to listen to the evidence against the 'victim' (in that case it was proven she was with her boyfriend at the time she says she was being raped). Many people treat him as a rapist and he spent 10's of thousands on an education he can't complete.
Other universities have free speech zones because people who don't want to get offended don't like hearing free speech all over campus.
When you let psychotic people with insane views get away completely unchecked you encourage those views and incorrect let younger people believe these views are acceptable by doing nothing to the person making them then 10 years down the line rather than an unimportant student union role she's ruining the life of people on campus, getting people expelled because she took offence to something someone said.
People like her should be held accountable, if they don't want to be held accountable they shouldn't take positions like head of the student union.