My understanding of the
opinion is that it voided that provision of VAWA because there was no
substantial nexus to
interstate commerce (required by the
Constitution in order for the federal government to regulate something). While, in my
opinion, the
decision is correct, there may be a
debate as to whether
violence against women affects interstate commerce.
Note that this does not mean that she cannot sue her attacker...it just means that she has to do it under state law.
Incidentally, you cannot say that O'Connor, Scalia, Thomas and Rehnquist always vote the same way, or for that matter always get it right. While they are certainly the most conservative, they regularly disagree with one another, and their decisions are not always consistent. Except for Scalia--who is consistently a little frightening (though often correct).