Percy Jackson's sister. The daughter of Gaia

When Sally had Percy, 9 months later, Paul had Calista Blofis. When he moves in with Sally with her, Everyone is happy. After an argument between Percy and Calista, Percy and Paul take Calista to her friends and they had a car accident. When Calista into a deep coma that she doesn't come out of for 2 years, what happens when Friction resumes? What happens when Percy finds out about her mum? What happens if she fights in the war? Against her mother?