Oh, no, maybe I'm allergic to you, Max.
— Maddy, Blue Detective
Although Maddy is part of a mean cheerleading squad, she is usually nice to people. Maddy could be seen as a girl who likes to follow popular girls as seen through her following Madison's lead and later on willing to be Phoebe's minion when Phoebe got the lead role.
Maddy and Max start dating. Max even tricks Barb into giving up her vintage bracelet to Maddy which makes Barb upset. Dr. Colosso becomes jealous of Max spending too much time with Maddy. Max takes Maddy out on a date at Splatburger. During the date, Barb sends Billy to super-speed into the restaurant and steal the bracelet from Maddy. Maddy goes under the table to look for it. As Maddy looks for the bracelet, Dr. Colosso comes for his revenge on Max and puts a blue bean on Max's sandwich. Colosso's fur causes Maddy to start sneezing, which disgusts Max a little. They are willing to put it all behind... until Max turns blue! Maddy freaks out when Max turns blue and runs away. Later at home, Maddy comes over to the Thundermans house to apologize to Barb for losing her bracelet. Barb takes the apology surprisingly well (because she already stole the bracelet back). Maddy freaks out for finding out that Max is still blue. She freaks out even more when she sees Phoebe has turned blue too. She concludes that Max's "blue disease" must be contagious. Phoebe feels embarrassed that a cheerleader from school saw her like that. Maddy resumes sneezing again and says that she's allergic to Max.
Maddy is one of the top cheerleaders that Phoebe and Cherry have to audition to in order to join the Hiddenville High Cheerleading squad. She is also one of the Madisons. Even though Maddy goes along with Madison's plan to embarrass Cherry in front of the whole school during the pep rally, it seems like Madison was calling all the shots. To get back at the Madisons, Phoebe only attacked Madison and didn't humiliate Maddy.
Max tries to get Maddy and her friend Roxy to audition for the lead role in the school play so that Allison doesn't kiss someone else but Maddy tells them that she has "stage rage" where she gets very angry on stage or by just thinking about acting on stage. When Phoebe gets the lead role, Maddy and Roxy easily accept to become one of her minions.
When Cherry disappears, Phoebe asks Maddy and Roxy if they've seen Cherry and they reveal to her that they saw Evan taking Cherry outside. This helps Phoebe figure out that Evan is up to something.
In Thundermans: Secret Revealed, Maddy is one of the girls helping Phoebe in setting up for the prom, along with Roxy and Cherry. The girls plan to go to prom together as "single ladies" even after the boys in Max's Band ask them out. When the fight breaks and the boys ask the girls who their crushes were, Maddy goes with Gideon.