Sometimes it takes a horrific and shocking event, such as the murder of George Floyd, or women speaking out against Harvey Goldstein to start a snowball effect. I think that this is one of those times, and whilst Sarah's family will mourn their daughter separately and remember her for what she meant to them, it is not disrespectful for others to be angry - about Sarah's death, of course, but also about all the other women and girls who are killed by men, and about all the things we all do in order to mitigate that risk.
I really don't think that Sarah's friend has any right to decide what Sarah would have wanted, or to dictate to others about 'politicising' her murder - there is surely very little chance that she and Sarah discussed their feelings on how they would want to be remembered in the event of their death by murder - how could the friend possibly know?
Telling people not to politicise events is another way of controlling them and dismissing their anger.
Slightly off the topic of the vigil, but as a related point, I keep hearing that 'it's not all men', just as we heard 'all lives matter', but IMO this misses the point in the same way as the ALM claims did. Nobody is saying that all men rape, or are dangerous, or need a curfew. It is fair to say, however, that the vast majority of violence (against men and women) is committed by men, yet when it is suggested that maybe men should have their movements restricted people react with outrage - not stopping to think that the status quo is that women have their movements restricted all the time.
Also, the whole rape culture thing works against men too. It results in the fact that women remain cautious about decent men - their colleagues, their friends, their neighbours. It demeans men by suggesting that they are unable to resist their sexual urges. No, not all men are rapists, but all men are being included in the assumption that women need to change their behaviour in order to avoid being raped. If people can't speak up for women, maybe they should think about that injustice against men, and speak up against that?