The reliance on foreign law actually makes sense here, which is why Scalia, who has condemned reliance on foreign law, joined the opinion (as did all of the court's conservatives).
The actual text of the Constitution doesn't help much here-- it says that a defendant in a lawsuit is entitled to "due process," i.e. to fairness, but doesn't get more specific than that. It is logical to say that it is not "fair" for a foreign corporation to get dragged into U.S. courts on a theory that foreign courts would never apply to U.S. corporations.
In context it was so superfluous and inept it actually did make me laugh. Like it was a rote or formulaic act by her.
BTW it was a relief that she didn’t look to the middle-east for her international example of ‘fairness’! Or China, Nigeria...