Absolutely Trivial (I think) but...BG? or Deidre?

OK, so i watched this atmospheric little gem, and all was good. Then I revisited the IMDB page, and saw that Rose Byrne's character is shown as "B.G.". I could have sworn I heard her introduce herself as Deidre, but I thought, I'm pretty much completely confused about half the time and half-confused the rest of the time, so I thought...'B.G./Deidre...maybe i just misheard'.

Then I visited a, ahem, alternative movie site, and, lo and behold, their synopsis referred to Byrne's character as 'Deidre' (although their cast listing simply called her "Girl"). So I guess I did hear 'Deidre'.

So, what's up with this? Is this a weird little trivia thing, a play to market sensitivities, or is it significant? Like, did I miss a level of duality in the movie or something?

Clara? Rose? Anyone? What's up?