Percy could be really angry. He might lash out at Annabeth and those involved. He has a fiery temper sometimes, and this would be a huge betrayal.
He could also be very sad and heartbroken. He's deeply in love with Annabeth, so this would be a crushing blow. He might isolate himself from everyone and just wallow in his pain for a while. He might also question all the memories they had together, wondering if they were all lies.
She could be extremely worried. In fanfiction, Annabeth might constantly fret over Percy's safety as Styx is a very dangerous place. She may try to find ways to reach him or send help.
She might be a bit shocked at first. But then, being Sally, she'd probably quickly regain her composure and give them a knowing smile. After all, she's seen Percy grow up and she would be happy for him to have such a close relationship with Annabeth.
She might be disgusted. Gabe is such a horrible person in Percy's life. So Annabeth could show immediate anger towards Gabe just from Percy's description.
Percy would probably be extremely hurt. He trusts Annabeth deeply, so this betrayal would shatter that trust. He might feel angry at first, wanting to confront both Annabeth and Luke.
Some of Percy's classmates might be in awe of Annabeth. She's smart and confident, so they could be impressed. Others might be a bit jealous that Percy has such an amazing friend.
Well, the nerdy classmates might be interested in Percy's adventures and keep asking him about the mythological creatures he's encountered. The jock - type classmates could be a bit more skeptical and might even challenge Percy to some sort of physical test, like a race or a strength competition. And the shy classmates might just peek at him from a distance and whisper among themselves about how cute he is.
It could also be due to some sort of magic or mind - control. A powerful enemy might have cast a spell on Annabeth, forcing her to turn against Percy. In this case, it's not really her own will but the result of external manipulation.
Well, one possible reason could be that Percy made a really stupid decision without consulting Annabeth first. Like, if he went off on a dangerous mission on his own when they were supposed to be a team. Annabeth is a very strategic person and she might feel betrayed or extremely frustrated by such actions.
Common reactions would include shock and disbelief. Since Annabeth and Percy's relationship is a significant aspect of the story, fans who are used to their connection would find it hard to accept such a fanfiction. Some might also be curious to see how the writer justifies this unfaithful act in the story, but overall, it's not a well - liked concept among the majority of fans.
Annabeth could be under some kind of magical influence. In the Percy Jackson universe, there are many magical elements. She could be cursed or charmed without her knowledge. This would be a very interesting take in a fanfiction as it would add an element of mystery and also give her a chance for redemption once the truth is discovered. Also, it could be that she has some internal insecurities that she hasn't dealt with and they manifest in this way, making her act out of character.