Seven half-bloods shall answer the call
To storm or fire, the world must fall
An oath to keep with a final breath
And foes bear arms to the Doors of Death
To figure out if Annabeth is part of the Seven we will need to look at all of these lines and see if she fits the prophecy. She answered the call; she joined the quest. Check. The second line is about Leo. So is the third. The fourth line, she along with her enemies, a Titan and a giant, went to the Doors of Death. Check. So it would seem as if she is one of the Seven. But some things don’t add up. Seven half-bloods answer the call.
She wasn’t called to join the quest. She asked Jason to bring her. Hera called on Jason by the exchange; same with Percy. Hera also called Leo from a young age. Percy asked if Hazel and Frank would come, so they also answered “the call.” But Annabeth asked to come. She wasn’t “called.” And the last line said that that foes would bear arms at the Doors. It didn’t say foes and friends. That would imply that Percy and Annabeth are enemies and they are not in any way, shape, or form. So if we take Annabeth out of the equation, it makes perfect sense. Demigods, like Percy, are enemies with Titans and giants. And the Titan’s show a slight rivalry (and the giants don’t seem to adore the Titans either) and hatred against the giants so it is foes on all sides. And there was plenty of demigods who went after the Athena Parthenos before Annabeth who succeeded so that doesn’t make her part of the Seven either. So if she isn’t one of the Seven, who is? Nico. Or maybe Reyna. Nico fills the requirement of answering the call. Percy made him swear to bring the Seven to the Doors on the other side. He agreed. And Reyna also answered the call because she was asked by Athena through Annabeth to bring the Athena Parthenos back and she did. Both fill the requirement to be part of the Seven. And both have been onboard the Argo 2 (which isn’t a requirement of the prophecy but it helps my theory).