Andrea starts a new year of elementary school with her best friend, Tammy. She becomes suspicious after repeatedly noticing Buddy's shadow passing by her window at night. She and Tammy follow him to the Putter home the night of Emma's party, where they spot Buddy with Molly (the Putters' female Golden Retriever) and realized that Buddy had been sneaking out at night because he is in love with Molly, eventually learning they're expecting puppies. Later, Andrea, Tammy, Emma, Josh, and Buddy rescue the puppies from Snerbert and Webster.
Andrea is initially too sad to go to the bus stop to say goodbye to Josh before he left for college, but with Buddy's help, she manages to get to stop the bus in time to say goodbye.
Starting her first year of middle school, Tammy and Andrea struggled to find an activity to join before both settles on trying out for the baseball team. Tammy was a natural but Andrea struggles at catching and hitting, running the risk of being cut altogether until Tammy, without Andrea's knowledge, convinced Coach Crenshaw that she and Andrea are best friends and if Andrea was cut, she wouldn't play either. Andrea became frustrated when she was benched for most of the season until Randy accidentally hit Tammy in the right elbow with a wild ball causing an injury and leaving her unable to play and Andrea replaced her. However, Andrea's first game in the season resulted in her running into Randy while trying to catch a pop-up fly, causing them to drop the ball and their opponent to win. Andrea came home and found that Josh's old room was being converted into a nursery for her baby half brother, Noah, and mentioned to Jackie that it felt like she and Josh were being replaced by him, but Jackie convinced her that it was not the case.
Andrea continued to struggle on the team and overheard Tammy confessing to Randy the deal she made with Coach Crenshaw when Randy wondered why Andrea was on the team even though she was terrible. Andrea wanted to give up on baseball until Buddy persuaded her to keep practicing, where she became better at hitting and catching. Andrea became the Timberwolves' pitcher and Buddy played first base (where Buddy was also revealed to be a great baseball player as well). Andrea and Buddy managed to send the team on a winning streak, but the day of their championship game, Carlton and Professor Siles kidnapped Buddy, with Tammy and Andrea in pursuit, rescuing Buddy, Zack, Striker, Shooter, and Duke before experiments could be conducted on them. The Timberwolves struggled without their three star players, but they managed to come back from behind to edge out their rivals, the Baboons, in an 8-7 game, when Andrea scored a double hit.
When Noah was sad about the Buddies having to go live with new owners, Patrick told him it was their time to leave, just like when it was Josh and Andrea's time to go away to college.