POSSIBLE SPOILERS BELOW (It could be right.. I don't know. I'm just guessing!)
Ellie: ".....hey wait.."
Ellie: "..hhhh...."
Ellie: "..Back in boston, back when I was bitten..."
Ellie: "..I wasn't alone."
Ellie: "My best friend was there, and she got bit too."
Ellie: "We didn't know what to do..."
Ellie: "So.. she says, 'yknow' lets just wait it out. We can be all poetic and just lose our minds together'."
Ellie: "I'm still waitin for my turn!"
Ellie: "Her name was Riley, and she was the first to die."
Ellie: "And then it was Tess, and then Sam."
Joel: "None of that is on you"
Ellie: "...No, you dont understand!
The Last of Us: Left Behind comes out on Valentines Day also.
Take a look at the last cutscene of the game and really notice Ellies body language upon talking about Riley.
From the very first moment, there's some kind of ..*coming out of the closet* feeling. As if she wants to say more but she isn't.
And since we know what happens to Riley, would it not be rather shocking if we actually realized just how much Riley meant to Ellie? Why else would ND tell us more about this story unless they had something very important to tell?
It is not impossible considering Bill was homosexual as well. Naughty Dog touched on a lot of *daring* subjects, this would not shock me at all.
Also take a look at the first minute preview of the Left Behind cutscene.
The fact that they aren't older makes it even more bold.
And take a look at the first minute of the DLC. Ellie thinks Riley was dead. She's kinda shocked and I don't know maybe I am just imagining that there is something more there.
Ellie: "I haven't seen you in I don't know how long..."
Riley: "45 days.. 46 technically."
Ellie: "All this time.. I thought you were dead."
Riley keeps count of the days even!
What do you think?