Percy's reaction could also be one of self - doubt. He may start to question his own actions and leadership. He might think that he has done something wrong to push Annabeth away. However, his loyalty to his friends and the cause would eventually make him stand up against Kronos and try to bring Annabeth back to the right side.
One possible reason could be that Kronos has somehow tricked her. Maybe he promised her something she desperately wanted, like power to protect her loved ones in a way she thought Percy couldn't. Another reason might be that she was brainwashed. Kronos could have used some dark magic or manipulation to make her believe that Percy was on the wrong side.
It could be for the greater good as she perceives it. Annabeth might think that by betraying Percy, she can save more people or prevent a greater disaster. However, her perception might be wrong, and she realizes it too late after the betrayal has already occurred.
Then, she would probably be angry. Annabeth is a strong - willed character. She would feel betrayed and used, and her anger would fuel her to find out the truth. She might start her own investigation to figure out what's really going on with Percy, whether he's been influenced by someone or if there's another reason for his actions.
One possibility is that it could lead to Percy's downfall. If Annabeth, who has been his close ally and friend, betrays him, it might shatter his trust not only in her but also in others. He could become more isolated and vulnerable, making it easier for his enemies to target him.
Well, in this fanfiction, Percy might face a huge moral dilemma. Since Kronos is a villain, Percy joining him could be a really dark turn. Maybe he's been tricked or is trying to stop Kronos from the inside. It could lead to some intense battles within the Titan's ranks as Percy tries to figure out his true loyalties.
If Percy Jackson joins Kronos in fanfiction, it would be a huge deviation from the original story. Percy is a hero who stands for good, and Kronos is a villain. This could lead to a very dark and twisted version of the Percy Jackson universe, with Percy using his powers to aid Kronos in his evil plans, perhaps causing chaos among the gods and other demigods.
When Percy joins Kronos in the fanfiction, it affects the other characters in many ways. Chiron, the centaur mentor, would be deeply disappointed. He had so much hope for Percy. The minor demigods who looked up to Percy would be lost. They might lose faith in the idea of being a hero. The relationships that Percy had built over the years would be shattered. His joining Kronos would also make the enemy stronger, which would put more pressure on the remaining good characters to come up with a plan to stop them both.
The story would be very different. The loyalty of the other characters would be tested. For example, Annabeth might be heartbroken and try to bring Percy back to the right side. Also, the gods would be in a much more difficult situation as they face a combined threat of Percy and Kronos.
Well, it could be that in the fanfiction, the writer might have developed Annabeth's character in a way where she becomes disillusioned with Percy. Maybe she sees Luke as having something that Percy lacks, like a different kind of power or charm. Or perhaps there are some misunderstandings between Percy and Annabeth that Luke takes advantage of, pushing Annabeth towards the betrayal.