Can someone clarify this part... (spoilers)

I have a question about the ending, when it's showing us what actually happened at the party. When Emily is walking around upstairs, she opens a door (before she knocks on the door where her two friends and the guys are) and there are two random girls sitting on the bed just looking at the door, right? Who are they and what's the significance of the scene? Is it just supposed to be like those guys could have actually chosen THEM but they chose Emily's two friends instead? Just making sure I'm not missing anything...