Have a list of resources handy. Provide them to your sibling. Rinse and repeat.

I am a professional, (not the PP). I can say that most often, the barriers are things like money, a place to say, being blamed for brining on the abuse, shame, not being believed.

If someone has these kinds of supports, it really is a matter of professional help and support groups becuase sometimes you need to hear it from others in similar situations to make it click.