It seems odd to me that they found her vehicle on the other side of the reservoir, across from the boat launch that was near the party. That would seem to narrow it down to one of 3 scenarios:
1. She drove into the reservoir in or around the boat launch (on the side of the lake by the party) and then the vehicle drifted to the opposite end of the lake near the shore.
2. She somehow ended up driving to the other side of the lake and into the water.
3. There was some sort of incident or accident and it was covered up by driving or pushing her vehicle into the lake.
Scenario #2 seems highly unlikely to me, as it appears it would be virtually impossible to drive to the other side of the lake without using Hwy 89 first. Even if she went the wrong direction on Hwy 89 and then exited at Hobart Mills Road (which then connects to Old Hwy 89, which eventually leads to the reservoir), it seems that she would have had ample opportunity to immediately get back on Hwy 89 in the correct direction.
How realistic would it be for her to enter the reservoir from the boat lunch (or nearby area) on the side of the reservoir near the party, and then for the vehicle to drift over to the other side of the lake? The map I'm looking at indicates that it's over 1000 feet from one side of the lake to the other (from around the boat launch to where her car was discovered). That seems like an awfully long way for a car to drift in relatively shallow water. Occam's razor, right? The car wasn't very far from the shore when it was discovered, so it would seem very likely that it went into the reservoir on that side.
If it's the case that the car went into the water on the opposite side of the reservoir, then I have a hard time believing that it wasn't foul play. As I already stated, it looks like it would be virtually impossible to drive a circuitous route around the lake to get to near where the car was discovered. One would most likely have to use Hwy 89 and even then there would be plenty of opportunity to make a U-turn (if that was even necessary) and get back on Hwy 89 in the right direction.
Remember also that we have no real evidence that KR was heavily intoxicated that night. Think about the source of those allegations.
I think we're still only going to get limited information about this case for a while, unless they determine it was clearly a simple vehicular accident.