The conflict between Bianca DeSousa and Katie Matlin started during Now or Never when Katie found out about her boyfriend's past with her and suspected a reunion between the two when he protected Bianca from Vince Bell. When Bianca thought the two would become friends, it turned out that Katie was just using her to get pills for her addiction. The two would often get into arguments with each other, but have recently put their past behind them and are frenemies.
Prior to Season 11, Katie hated Bianca for her reputation, like most girls at Degrassi.
In Mr. Brightside (2), Katie becomes aware of what happened with Vince and his gang. She already doesn't like Bianca for putting Drew into that situation.
In Dead and Gone (1), Katie is in charge of 9th grade orientation and pairs Drew up with Bianca, so Drew could find out what was going on, making her jealous of the two. Drew confronts Bianca about Vince by locking her in the room, and wants to no what her and Vince are planning. Bianca tells him about how Vince forced her into a relationship, and if she breaks it Vince will go after him. She also shows him the bruises Vince gave her, and Drew promises to help her. He later invites her to Prom so she can get away from Vince. At the end of the day, Katie finds Drew furiously hitting a punching bag, making her worried. She asks him what's going on, and Drew tells her that Vince is physically and mentally abusing Bianca in trade for sparing his own life. Katie tells him that fighting won't fix anything, but Drew doesn't listen to her.In Dead and Gone (2), Katie goes to prom with Drew, but is upset when she find out he invited Bianca. Katie asks Drew why she is there with them, and Drew tells her Bianca is there to keep her safe. Katie is still mad, but tries to get over it. Drew talks her into trying to get along with her, and Katie tries, but Bianca shuts her out once Katie sees Vince's bruises on her wrist under her bracelet. Katie tells Drew this is not the way she thought prom would go, and Drew asks her to dance. While dancing, they and see Bianca and Adam dancing, making them happy. Katie realizes she was wrong about Bianca, that she actually isn't so bad. Vince shows up and Bianca tells Adam, Drew and Katie that she will handle it. Drew tries to go after her, but Katie asks him to stay with her, and he agrees. Vince grabs Bianca, and Drew walks up to Vince, telling him to go. Drew beats up Vince, and starts to walk back to Katie. Vince gets up with a gun and shoots two bullets randomly. After the shooting, Drew makes sure Katie is okay, and they both realize it was Adam who got shot. They both comfort him, and Katie uses the steps she learned in a class to save Adam's life. Katie notices Drew goes after Bianca, and Katie tells him that he doesn't stand a chance against guns, but she decides to go with him. She watches as Drew calms Bianca down, and Drew comforts her as Vince gets arrested. She then goes to the hospital in the morning with Drew and Bianca to visit Adam. Drew then gives her a hug, happy that she saved Adam.
In Nowhere to Run, Katie gets worried and jealous once she finds out that Bianca has been staying at Drew's. At the cabin once Bianca shows up Katie gets a lot more jealous and paranoid and keeps accusing Bianca of trying to steal Drew from her and Bianca tells Katie her jealousy is just going to mess up their relationship.Katie also reminds Bianca of when Drew cheated on Alli and that she won't let it happen to her. When Katie goes outside with Marisol so she can smoke weed, Katie makes fun of Bianca's name when they are locked in the outhouse. When they return Katie accuses Bianca of locking them in. The next day when they all leave Katie has Drew walk Bianca to her car. Marisol asks why she'd do that and Katie says she's just getting used to them becoming friends.
In Hollaback Girl (1), Katie seems annoyed when Bianca finishes her test before her, then when Bianca sits down to file her nails and Katie reminds Bianca she's still taking her test and Bianca sticks her tongue out at her at which makes Drew laugh. In the halls Katie agrees to help Bianca out. When Katie is helping out Bianca she asks where she had scored drugs. Bianca replies by telling her about her connections and doesn't hang out with that crowd anymore. Katie suggests they have a girls night. Later they go to a club and Bianca tells Katie to tone it down once Katie asks if the fake ID's will fool them. And Bianca makes Katie show a bit more and Katie says she's sorry she didn't have slut wear and Bianca just shrugs it off with a laugh. When a dealer tries talking to Bianca she ignores him and Katie goes off and tries talking to him, but Bianca stops her and they dance together. When it's Bianca's curfew she tells her to go home and finds Katie high and dancing with the dealer. At the Matlin household Bianca realizes that Katie only wanted to hang out with her for drugs and Katie says she's been waiting months to steal Drew from her, Bianca calls Katie a mess and Katie gets catty and starts firing back insults at Bianca who sprays her with water and Bianca leaves.
In Hollaback Girl (2), Katie is home after being in the hospital for overdosing. Katie blames the whole thing on Bianca, and Drew takes her side, in which Bianca can't believe and Drew tells Bianca to go. When she spots Drew and Katie outside the office, she reminds Katie that Drew will be there for her.
Season 12In Come As You Are (1), Katie, Drew, and Bianca are seen at the school assembly together. Katie and Bianca have a short chat. Katie laughs when Bianca takes off her shirt.
In Come As You Are (2), Katie and Marisol run into Drew and Bianca at the mall. Tension is high, but Katie walks away without telling Bianca what happened between her and Drew.In Gives You Hell (1), Jake offers to help Katie after her break up with Drew. He tells her that she just needs to get her anger out, and they go to Drew's house to throw eggs at his window. But when Katie finds Bianca's car there, she throws all the eggs at her car and breaks her side mirror, forcing Jake to pull her away and run. The next morning, Bianca is seen fixing her car with Drew and Adam when Katie walks by commenting on it. Bianca yells at her and the two almost fight but Drew and Marisol stop them, Drew tells Katie to stop and move on and leave Bianca alone. Later when Katie is putting together the hockey team tape Dallas gave her, she finds footage on there of Drew stumbling drunk and joking about how he slept with Katie, Katie is furious and uses the footage during the school pep rally, putting Bianca into rage and dumping Drew. This pleases Katie.
In Building A Mystery (1), Katie gives Bianca a look as she walks past her and Fiona.In Degrassi: Las Vegas, Bianca and Katie end up aboard the same flight to Vegas. Drew invites Katie to their wedding, which upsets Bianca, who refuses to speak to Drew for the rest of the flight. Later after Katie and Jake break up and Drew leaves Bianca at the altar, the two talk on a bench outside. They drink a bottle of champagne that Katie brought as a wedding gift and then talk about Darrin Howe's pursuit of Katie and Bianca's worries with Drew. During their talk, Katie convinces herself to go to Darrin's room, but as Katie leaves, the girls appear to be on better terms.
- Katie is the second girl to be enemies with Bianca because of Drew. The first is Alli.
- They were both love interests for both Torres brothers.
- Both girls dated Drew Torres, and both have had sex with him.
- Bianca actually wanted to be friends with Katie in Hollaback Girl.
- Bianca was extremely upset that Drew invited Katie to their Vegas Wedding.
- Bianca and Drew attempted to have sex before, and Drew wanted to lose his virginity to Bianca, but he actually wound up losing his virginity to Katie.
- Both are friends with Adam Torres and he has had an attraction to both girls.
- Both went to Jake Martin's cabin in Nowhere to Run.
- Both girls took drugs.
- Bianca took psychedelics (mushrooms) and Katie took oxycodone. However, Katie developed an addiction while Bianca used drugs for recreation and was not addicted.
- Bianca has also had a conflict with Katie's best friend Marisol Lewis, while Katie has had a conflict with with Bianca's friends Fiona Coyne, Imogen Moreno, and Mike Dallas.
- They both graduated in the Class of 2012.
- Bianca told Katie and Marisol to smoke weed they found in the couch in Nowhere to Run.
- They both attended universities after graduation.
- Bianca attended Wilfred Laurier University and Katie attended Stanford University.