Why does she care?

“De quoi s’occupe-t’elle ?”

Implying that you are thinking that she should mind his own business: “Elle devrait s’occuper de ses oignons” (idiomatic expression).

I can’t help them if they don’t care.

“Je ne peux pas les aider s’ils s’en moquent” or (slang) “s’ils s’en foutent”.

To care about one’s community

“Prendre soin de sa communauté”