The last girl?

This is a question for the people who 'got' the movie and the various layers of symbolism you have to work through to comprehend it.

While the movie came into focus for me on multiple viewings, there's something about the ending that I can't make sense of.

Towards the end of the movie Rick is seen with the latest addition to his string of female partners. However, she is the only one whose face we never see or voice we never hear. She is not a character so much as an anonymous female presence.

Also while the camera tends to focus on and linger on the bodies of his previous partners, the scene in which we see this one swimming naked in the pool allows her to swim past and then lingers on the water (one of the most beautiful images in the film, to my mind).

One of the things that isn't apparent in the first viewing of the movie is that some of the scenes are not literal events on the film timeline - these include Rick's father washing his hands in blood and the scene where Natalie Portman's character is surrounded by angels.

I suspect the final girl might be similar - symbolic rather than real. After all up to this point Rick's entire journey has been to see that these women are incapable of providing him with the solace that solitude and reflection provide.