The Seventh Half-Blood

Warning! May contain Lost Hero and Son of Neptune spoilers!

Ok, so we all expect it to be Annabeth, right? I kind of do, but I'm not quite sure. What makes me unsure is this line:

"Wisdom's daughter walks alone, the mark of Athena burns through Rome."

Technically, the only confirmed people of the seven are Jason, Piper, Leo, Percy, Frank, and Hazel. (Only two girls?!?!)

Now, I'm sure that for some people, it became "obvious" that the seventh is gonna be Annabeth when Ella recited that line, or when the first chapter of MoA was told from her POV. But if she's going to walk alone, does that mean she can't be part of the seven?

Couldn't the seventh be someone else? Like... I don't know, Reyna? I would say Octavian, but he's a legacy, not a half-blood. (The lime does go, "Seven half-bloods will answer the call") Odds are, if it's not Annabeth, it's most likely a Roman camper.

Maybe when the story is told from her POV, she's "walking alone". Maybe she's doing whatever she has to do with this "mark of Athena". From the summary of Mark of Athena, it doesn't sound like Annabeth is going to be in a very pleasant situation. Perhaps she'll be forced to not be one of the seven and go in her own path.

Or we could go back to what I first said. It could be Annabeth. It probably is too, especially with all this fuss over the Percabeth reunion we've all been anxiously waiting for. ;)