On the other hand, Percy might also try to win her back. He could start by reflecting on his own actions and try to figure out what went wrong. Then he could set out on a journey to find Annabeth and convince her to come back. He might bring gifts or do heroic deeds to show her that he's changed or that they still belong together.
He may become angry. Percy has a bit of a temper, so he could lash out at the situation or even at Annabeth if she's still around. He might feel betrayed and start to question all the things they've been through together. He could also go into a state of depression. Losing Annabeth, who has been such an important part of his life, could make him withdraw from his friends and activities. He may lose his motivation for quests and just mope around, feeling sorry for himself.
Percy is likely to be heartbroken. He may initially be in a state of shock, not being able to believe that Annabeth has left him and their daughter. He might feel angry as well, feeling betrayed by her sudden departure.
Percy might be a bit flustered and embarrassed. He's protective of his relationship with Annabeth, so having Magnus walk in might make him feel like their privacy has been invaded. He could quickly try to shield Annabeth or just look really shocked.
She might be heartbroken at first. She could try to jog Percy's memory by showing him things that were important to them.
Annabeth could also be angry, not at Percy but at the situation or the forces that led to his death. She might vow revenge and start on a journey to find out who or what was responsible for Percy's sacrifice and make them pay. This could lead her into a whole new set of adventures and challenges as she tries to come to terms with her loss.
She'd probably be shocked at first. But then her face would light up with joy. After all, she and Percy have been through so much together.
He could also become withdrawn and depressed. Percy and Annabeth have a very strong bond, and her death would leave a huge void in his life. He might isolate himself from his friends and family, lost in his grief and memories of her.
He would probably be shocked. Percy has always trusted Annabeth, so being stabbed by her would be completely unexpected. He might initially be unable to believe what's happening.
At first, Percy would likely be angry. He's a fighter, and being betrayed by someone he loves would fuel his rage. He might go after Annabeth to demand an explanation. But as the reality sinks in, he could become very sad and withdrawn. He might isolate himself from his other friends as well, feeling like he can't trust anyone anymore. He would constantly be thinking about what he did wrong to make Annabeth turn on him.
Annabeth would likely be furious at first. She has been through so much with Percy, and for him to leave her for Calypso would seem like a betrayal. But then, she might also start to reflect on their relationship and what went wrong. She could become determined to win Percy back or to move on and prove that she doesn't need 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.