Smileless - I am sorry to hear about your headache but pleased that it has shifted. Be kind to yourself. xx
Grandmasosad - I am so sorry, that must be terrible, especially as you have had so much contact until recently. It's awful for the DGC too, who must be missing you terribly. I am sure that they will have been asking to see you and your husband. I am sure your DD must be missing you too.
It sounds to me as though your daughter is having problems with her mental health, as her reactions go way beyond what's normal. She may disagree profoundly with your political views, but that is absolutely no excuse for assaulting you.
The problems do seem to have built up since she married your SIL and I assume that he is not the father of your DGC. Never underestimate the power and influence a spouse or partner has in a relationship. My estrangement from my oldest DD, fortunately now healing, was instigated by my SIL. I know this, but what I can't understand is why DD went along with it.
In your case, from what you have said, your DD seems to be easily influenced, as she swapped her political views from yours to SIL's, when she is of an age to have her own views. I have the opposite problem with my DD in that she and SIL hold various views which I find abhorrent, whereas DH and I are more liberal, and my other DDs are 100% 'woke'! We studiously avoid potentially contentious conversations with DD1....!
You mention George Floyd and BLM, so you probably realise that this issue has aroused very strong emotions, so I would advise you to tread carefully. If you go onto the Mumsnet website, you will see that politics and other issues about which people hold very different views, have caused a lot of divisions within families. I was reading a thread a few days ago, where the DIL wanted to cut off her MIL because she disapproved of her views and didn't want the DCs to be contaminated. What surprised me was that the majority of posters thought that she was doing the right thing, whereas the minority said that it was wrong to cut GPs out because of a difference in political views.
I have been educating myself about 'white privilege' recently, encouraged by my younger DDs, as I like to be well informed on current issues. I do think that it is something that many white people do not fully understand and that everybody carries prejudices to a greater or lesser degree, whatever their nationality, religion or skin colour. The prejudice can be compounded if we are surrounded by people who share our views, a sort of 'echo chamber'. I would hate it if my DC or my DGC thought of me as racially prejudiced.
So, in your shoes, I would step back for a while, although I know that this is difficult. Do not chase her or take any actions which could be regarded as harassment. You have a strong relationship with your DGC and, given their ages, I feel sure that they will be back in your lives - it's just a matter of time. I also feel that your DD will be needing you soon too.
In the meantime, maybe you could read around some of the issues which have caused the disagreement, so that if and when there are any future discussions, you can respond from a position of knowledge and understand her views, even if you don't share them.
Good luck 