AIDS metaphor film

Pretty clever. The girl who comes to the cabin single has AIDS, and spreads it as she "bites" the various males. That's why the young girl, the virgin, "can't let her boyfriend in" (get it?) at the end, after he's been "bitten" by her. She survives because her blood was never tainted. Likewise with Kim -- that's the significance of the final lines, where the AIDS predator Eve says, "I f---ed your boyfriend" (meaning, "Your dead because you've been sleeping with someone tainted by my blood"), and she replies, "We were broken up," meaning, "I wasn't sleeping with him anymore, so he didn't pass on the disease to me; I win."

John Carpenter did something similar with The Thing in 1982. Very similar, in fact.