My sister has blocked me

Not sure what/why you would want to do/deal with this?
Your very strained relationship seems to have been based on you keeping your mouth closed whilst a tone deaf, insensitive and bombastic person sounds off about any subject she chooses, with no respect for the feelings or opinions of others. Bet you'd never have tolerated this for years if this was a 'friend'. Family often believe they are untouchable!

I'd do absolutely nothing. If she reappears, you have a chance to lay down some new ground rules before she assumed that everything can be put right between you. If she doesn't - well there must be so many people you'd rather spend time with. Life may be too short to quarrel, but it's certainly too short to waste on those who don't value you and your feelings.

The comment about your friend's 16 year old son would be enough for me to block her! What a bl**dy wicked thing to say!!

Is she someone you would have as a friend? you do not have to have a relationship with someone just because you are blood-related to them.

aonk

A detrimental comment about Prince Philip especially just after he died would be unforgivable to me.

A comment about a severely disabled 16 year old having to die sometime would be unforgivable to me.

Honestly OP your sister sounds dreadful. I would enjoy the quiet. If she reappears on social media put her on limited profile. If she says offensive stuff just say you don't want to discuss.

You can still love her while accepting she is somewhat stupid.
May be best thing is to accept her like you accept a child who does not know any better. It is unlikely you will be able to educate your sister.
Can you tolerate her stupidity?

I would just avoid politics. You hold very different views on things, but that’s not to say you don’t love her as a sister with your shared history. My sister and I are different and we agree to differ, we had years apart but I can honestly say despite our differences we love each other. I don’t know why your sister makes cruel comments, surely she doesn’t mean them, that’s nothing to do with different political views, it’s like saying all labour supporters are the kind ones and Conservative supporters the opposite which clearly is not the case.there is good and bad in every aspect of life. We can’t all think and be the same.