No one gets a perfect score on a test--I know from experience, and I'm sure in his undergrad days, Rob botched an exam, too. You chalk it up to experience, and learn from it. You may have failed the academic part of the test, but its what you do with it when you apply that failure to the rest of your life that matters here, so study and do better next time
About Mexico, I'd be disinclined to head south of the border. Even a place like Aruba with its close connections to the Netherlands isn't a place I'd be happy to let my nieces go to (I do wonder if the Aruban or Dutch authorities would have put more emphasis on Ms Holloway's disappearance had they known that she is/was a relative of Teddy Roosevelt?). I'd be especially disinclined to approve of a trip south of the order for a young blonde woman with, ahem, ample virtues, but as I've never been south of the border myself, I can't really speak from experience, and what I do know from reports actually has a lot more to do with TJ than along the AZ or TX border or from Cabo or Yucatan. But Texasdrake made a very, very (VERY) good point about never leaving your drink, soft or alcohol, unattended. For that matter, you shouldn't do that here, either--plenty of date rapes or acquaintance rapes happen off campus among students.
And as far as the whole taking your family to work thing goes, well, you run the gambit from Mike and Shelby Hodges, who screen their daughter's non-sex scenes and give her feedback, to what a distant relative of mine did (who is in the business) founding Parents in Adult, to to what you encountered with your sister where academia hit reality. Its not always easy to know how you're going to react to something until you actually see it for real. To be honest, I've been thinking about how I'd react were I in either of your places, and I'm not sure, but I know either way I'd be anxious, on the one hand about being judged, betrayed or ostracized, and on the other hand about someone I care for maybe being exploited, hurt mentally or physically or, again, being judged by others who don't know the whole story. Knowledge is power, but sometimes the difference between what you know, or what you think you know, and what's really going on can be a big shock as I assume it was for both of you. So taking a break from each other for a while isn't so bad, and when you two are ready to talk (or not) you can. Que sera sera, whatever will be, will be.