Complex sentence: When Jessie insults Kristy but then realizes she is wrong about who the female wrestler likes, she joins forces with Zack to convince Kristy to rejoin the team, and Zack resumes dating her.
Split into simpler sentences: When Jessie insults Kristy, Jessie then realizes she is wrong about who the female wrestler likes. She joins forces with Zack to convince Kristy to rejoin the team, and Zack resumes dating her.