The amount of people who are all giving “reasons” why they are gonna be ok to treat others with contempt and apathy towards any suffering just means you wanted an excuse to not care all along, not that you are morally superior.
You will still look like an asshole to anyone that isn’t informed and to the people who didn’t agree with you in the first place.
If you actually care you keep trying, stop pretending minute crusades are anything but.
Being apathetic towards someone’s suffering doesn’t mean I’m cheering for it, that’s just psychopathic. However, I’m not going to lose any sleep worrying about your sister’s situation. If she needed help (and would accept it), that’d be different, but it sounds like she won’t. I’m sorry to hear about her situation, though.
That said, if she was my sister, rather than a random stranger, I’d be a lot more invested, so I can empathize with your situation, wanting to help her but being unable to reasonably do so.
I also won’t claim I don’t experience schadenfreude when I read an article about someone who (for instance) voted against their self-interests being negatively affected by the result of that action, but I’d still prefer that nobody was put into that situation in the first place.