How do you deal with "toxic" family members?

[Mantoinette]

One of my sisters is in her 30s and lives a lifestyle nearly the opposite of her strong Catholic upbringing, and it even seems to border on (or actually be) what is considered sociopathic. She seems to have no conscience, no guilt, no empathy, etc. ... yet she feels entitled to all sorts of attention and support in return while she continues to live a reckless, selfish, irresponsible, and godless life halfway across the world -- presumably to more effectively "hide" it from us.

So, for example, in a case where a father abuses his child, are they actually expected to just accept it in the end and do their best to just get along be civil to one another? If your husband carries on an illicit affair with your best friend, do you just turn a blind eye in order to keep the peace and not sever the friendship and marriage? When trust is completely gone forever, do you just try to imagine that maybe you're wrong or that hopefully things will change? Is that really what God wants?

How do you do you deal with a toxic relative?