I think they would freak out if they supplied her the drugs. That can get you charged with a felony in many instances. Thinking about going through that and having it on your record could be a very, very scary thing for a college kid.
As for the body...I went to two different colleges far from home and I know experience with the surrounding area is not uncommon. The area's recreation spots, lakes and quarries are the obvious choices in Indiana. Obviously we've seen lake searches for Lauren already. They also know how to get out of town and there is the possibility they just put her in a wooded area not far off the road. That has happened in other cases.
I have a vague inkling that what they'd do is hide the body indoors and transport it somewhere slightly more familiar at a later date. Which is what makes JR and JW's skipping out of town more troubling.
For me, if I was involved in drugs, I'd get rid of my stash, drag the body to the bathroom, and call the cops. Then I'd act really surprised that she'd done drugs in my apartment when all I'd given her is alcohol, and just take the underage/supplying a minor charge that I'd already had. Or just drive her to the emergency room and beat it.