Bianca is very concerned about her appearance as she can be seen putting on things like perfume and beauty powder. She's very beautiful, elegant, and graceful, which sets her apart from other Disney females. Despite her slight obsession with her appearance, she is very kind-hearted, compassionate, caring, and very unshallow. It is also shown that she is quite daring and has a love for adventure, as shown in certain scenes in the movies. She also has a strong sense of duty when it comes to her position in the Rescue Aid Society, placing her duty before anything else.
Miss Bianca arrives late at the Rescue Aid Society headquarters as they are singing their song. Before heading inside, she sprays herself with perfume and notices Bernard looking at her. Once she heads inside and starts singing along, the male members all turn and watch her with interested and respectful expressions. She sits down and the chairman calls forth the Mouse Scouts to bring a bottle containing a message. Bernard is called forward with a comb that is to used as a ladder to retrieve the message inside the bottle. Bernard nearly hits the chairman, Bianca and the other Society members. After Bernard pulls the message out of the bottle, the chairman tries to read it, but has trouble doing so. Bianca, however, is able to read the message and determine that it was written by a girl named "Penny." Showing concern for Penny, Bianca begs for the chairman to let her have the assignment. The chairman is hesitant at first, but decides to let her go as long as she has a co-agent. Many of the male Society members volunteer, but ultimately, Bianca chooses Bernard, believing that the two of them will be a great team.
Bianca and Bernard begin their search for clues at an orphanage where Penny once lived. Inside the orphanage, they meet a cat named Rufus. Rufus explains that the last time he saw Penny was after she did not get adopted by couples visiting the orphanage. He goes on to say that Penny had been offered a ride by a sinister woman named Madame Medusa, the owner of a trashy pawn shop near the orphanage. Rufus believes that Medusa is most likely responsible for Penny's sudden disappearance.
Next, the team go to Medusa's Pawn Shop. The shop is empty when they first enter, but soon Bianca finds one of Penny's school books. Bernard reasons that Penny must still be hidden somewhere in the shop. However, before they can investigate further, the telephone rings. The mice quickly hide as Madame Medusa enters and answers the phone. The mice overhear a conversation between Medusa and her accomplice Mr. Snoops. Medusa immediately asks whether Mr. Snoops had found "the diamond". When Snoops reveals that he had not and that Penny had been sending messages in bottles, Medusa is angered and decides to fly to Devil's Bayou that very night. Bernard stows away in Medusa's suitcase as she carelessly packs. Bianca tries to get in the suitcase but cannot and ends up riding on the floor of Medusa's car as it speeds down the street. The car (a convertible) makes a sharp turn and the suitcase falls out taking Bianca and Bernard with it
Although Bernard protests due to the abundance of the unlucky number 13 on the flight, Bianca flies with him on Orville the albatross to Devil's Bayou. When in the process of landing, Penny escapes from the clutches of Madame Medusa, so she releases her 2 pet crocodiles, Brutus and Nero, to find her as well as going out in her swampmobile. She orders Mr. Snoops to set off fireworks to illuminate the swamp for her. Orville is hit by one of them and crashes, although the two mice are unhurt thanks to Miss Bianca's umbrella. They meet up with two friendly bayou mice who would like nothing more than to rid the swamp of Madame Medusa and witness Penny being recaptured by Brutus and Nero. The bayou mice lend them their dragonfly Evinrude to use as a motorboat.
When they arrive at Madame Medusa's pirate ship hideout, they hide from Medusa and her henchmen, but as Brutus and Nero are passing them Brutus smells Miss Bianca's perfume. He and Nero chase Miss Bianca and Bernard through the ship and ultimately into a large organ. While in there, Brutus/Nero, whichever one starts playing the organ which causes Bernard and Bianca to float up out of it in their attempt to eat them. Finally, Bernard flies out of the organ and Brutus/Nero catches him in his mouth. Medusa then arrives, telling her pet crocs to stop with the noise and hits Brutus/Nero with her cane causing him to spit Bernard out. Medusa then freaks out and attempt to kill him and Bianca along with Snoops by shooting them. When Medusa's gun stops shooting, Bianca and Bernard take the opportunity to run, only to be shot at the last minute by one of Medusa's bullets. Luckily, the two survive and end up in the bayou and are found by Evinrude.
After being rescued, Bianca furiously wishes she was big enough to take on Medusa by saying quote, "Oooooh, if I was only a ten foot mouse, I'd show her." Bernard then doubt that he and Bianca can rescue Penny because they are merely two little mice, but she reminds him that the Rescue Aid Society is depending on them and that they can't quit after hearing the theme song in her head.
Bianca and Bernard see Penny out on the balcony of the ship. When she goes inside to her room, the two mice observe her from outside of a window as she prays. As Penny starts crying, the two mice are now inside and meet Penny and Bianca tells Penny not to cry because they have come to help her. Penny seems excited because her message (that was sent earlier in the beginning of the movie) had reached someone, but them she asks why she and Bernard didn't bring someone bigger with them (such as the police). Bianca then declares that the three of them should work together and have a little faith.
Together, Penny, Bernard and Bianca concoct a plan to escape the bayou that night by first trapping Brutus and Nero in an elevator, followed by escaping in Medusa's swampmobile and keeping her preoccupied by shooting off Mr. Snoops' fireworks in her room.
With the plan in motion, Bianca tells Penny to get dressed so they can put the plan into action. Bernard tells Evinrude to get Ellie Mae and the other swamp critters, but the plan is put on hold when Evinrude is cut off by a swarm of bats.
In the Black Hole, Bianca along with Bernard and Penny set off to find the Devil's Eye. Bianca is dreaded by the appearance of the cave. Penny informs her that it as once a pirate's cave. When Bianca asks Penny how she knows this, she answers by showing her the skeletal body of what was once a pirate with a sword stabbed in its chest.
After rescuing Bernard from falling into a dark hole in the cave, Bianca and Bernard continue to search for the Devil's Eye. When Penny holds her lantern up to a skeleton's head, they discover the Devil's Eye inside of it. The two mice try to get the diamond through the skull's left eye, but the diamond is too big. Luckily, with the help of Penny and a pirate sword, they are able to get the diamond out of the skull through the mouth and just barely escape the cave after the tide comes in and nearly drowns her, Bernard and Penny in a whirlpool.
Later, Medusa is about to escape Devil's Bayou with Penny's Teddy bear (which she has stuffed the diamond inside of), but Bianca and Bernard trip her with a rope.
After Penny manages to get her Teddy bear back and commandeer Medusa's swampboat Bianca is seen attempting to help her start the vehicle.
Bianca made occasional cameos on House of Mouse.
Bianca, along with Bernard, made appearances at Walt Disney World and Disneyland in the years following the original film's release. They currently don't make appearances at the American parks, although she and Bernard continue to appear regularly at the Tokyo Disney Resort.
- Miss Bianca's Hungarian personality comes from her voice actress, Eva Gabor, who was born in Hungary.
- Her voice actress Eva Gabor has also voiced Duchess.
- "Bianca," which is the singular feminine form of "bianco," is Italian for "white," appropriately describing her fur color.