Mrs. Frederickson is known to hold a rivalry with Binky Mole at least since Fred was a child because of his behavior around her, as Fred did not know about their snob lifestyle.
Both Mr. and Mrs. Frederickson constantly go on vacation, usually leaving Fred alone at their mansion.
She is a posh woman who is part of San Fransokyo's snob society. Still, she does not seem to have any problem with Fred's disregard for luxury and love for fiction and comic books. The only time she cared about Fred looking fancy was when it was time for his bro-tillion because she wanted to leave a good impression on Binky.
Mrs. Frederickson is noticeably younger than her husband. She wears makeup and has brown hair. She uses white pearl earrings.
As a fancy woman, she has different outfits that she switches depending on the occasion.
Mrs. Frederickson does not appear physically in the film, but pictures of Fred and his parents can be seen at different places on their mansion. One of the portraits also hid Mr. Frederickson's secret superhero lair behind it.
In "Fred's Bro-Tillion", Fred called his team as an "emergency". They got to his house quickly, but simply saw him getting his toenails done by Heathcliff. Fred told them it was time for his bro-tillion and explained it was an event in his honor to introduce him to San Fransokyo's rich families. Mrs. Frederickson came into his room to measure him, explaining to his friends about Binky Mole and their rivalry.
Hiro helped Fred out to get ready by going back to create a dance chip for Baymax. While Fred and Baymax danced, Mrs. Frederickson entered worried telling Fred that there was an avalanche at their family mountain and his father was helping out there, thus unable to attend the event. The bro-tillion however wasn't cancelled, and Heathcliff told Mrs. Frederickson that their caterer had cancelled even though Mrs. Frederickson said she'd pay him a great amount. At another room with Heathcliff, Fred's mom started worrying about it, but Hiro then offered a "hot new caterer" for the party, telling Fred's mom that she'd be on the cutting edge. Mrs. Frederickson thanked Hiro and hugged him, calling him a lifesaver.
Later at the party, she introduced her son, who was nervous and asked Baymax for help. The party was soon interrupted by Baron Von Steamer, who emerged from the ground with a giant drill vehicle. Mrs. Frederickson told him that he was not invited. Von Steamer claimed he was gonna kidnap Fred, and Fred simply felt relieved he wouldn't have to dance. Everyone started running and leaving, but Mrs. Frederickson only cared about Binky's impression, who was also leaving looking angry.
Von Steamer took Wasabi hostage, mistakenly believing him to be Mr. Frederickson's son. This led Fred and his friends to leave the event and save him, but once Wasabi was back to safety and Steamer was defeated, they went back to the bro-tillion which was now held in a smaller scale at Lucky Cat Café. Binky still attended and was grumpy the whole time. Fred danced with his mother and she claimed that she liked the current party better, also saying it was time they stopped worrying about what Binky thought about them, then telling her son she was proud of him while Fred looked at Baymax, who helped him with the dance steps.
Sometime later, a rich investor called Orso Knox was supposed to go to the Frederickson mansion for dinner, so Mrs. Frederickson called Fred while he was reading comics with Mini-Max to get ready for the visit. However, a mysterious monster soon broke into Fred's room and destroyed everything, but left shortly after and then Mrs. Frederickson entered the room, seeing the wreck but only telling Fred he hadn't changed his clothes yet.
Fred's friends arrive to help clean up the mess with Heathcliff while Mrs. Frederickson watches. Later the team discover that the monster was Orso Knox himself, who somehow had turned into a beast.
- It's unknown whether she is aware of her husband's secret superhero identity or not.