In the long run, Percy might grow from the experience. He could become more cautious in his relationships and less trusting. Or, if there's a chance for redemption in the fanfic, he might be open to forgiving Annabeth if she shows true remorse and has a valid reason for her actions. But initially, it would be a very difficult and emotional time for him.
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.
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.
Percy would be extremely hurt. Sally is his mother, and her betrayal would shatter his world. He might initially go into denial, not wanting to believe that she could do such a thing.
He could become withdrawn. Percy is a sensitive person at heart. So if Annabeth's actions are really hurtful, like if she cheats on him in a fanfic (although it's a very sad scenario), he would likely isolate himself from her and their friends. He might go off on his own to think things through and deal with his pain privately.
Annabeth might be initially in awe of Percy's new godly status. But she would quickly start thinking about how to use this new situation to their advantage. She is practical, so she would likely start planning how they can better protect their friends and the world.
She might be initially very angry. Annabeth is intelligent and perceptive, so she would likely feel betrayed that Percy thought he could deceive her. For example, if Percy lies about a mission, she could find out the truth later and confront him immediately, demanding an explanation.
She might initially be shocked. Annabeth is a strong character, so she could start by trying to stand up to Percy verbally, asking him why he's being so mean.
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.
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.
Annabeth could be annoyed. If she doesn't understand why Percy is staring, she might think he's being rude or wasting time. So she could give him a sharp look or a sarcastic comment to snap him out of it.