I remember watching part of a horror movie where some teens were somewhere in Europe at a fake party that was actually planned to find people to kill. I remember this girl in a row boat with a "nice guy" that ends up trying to kill her. Any ideas?
This sounds to me like Hostel: Part 2. The three main characters (all female) go to a local Harvest Festival. One of them, Lorna, gets intoxicated and goes for a boat ride with a nice guy. He ends up kidnapping her and selling her to a woman who ends up killing her and using her blood for a bath.