In "Touched by an 'A'-ngel," when Hanna goes to try on bridesmaid dress and bumps into Kate in the store. When Kate sees Hanna trying on her dress, she sweetly expresses her disappointment that they couldn't all try their gowns on together. Before meeting her, Mona_Vanderwaal formed a negative opinion of Kate, based on what she considered a hideously ugly gown. However, when she sees Kate, she notices a rare designer piece that she is wearing. Kate invites Mona and Hanna to lunch, and Mona accepts, while Hanna declines. Kate seems to hear Mona only, and they set a date.
Later, the three are seen together on a horse farm, instead of a restaurant, because Mona mentioned going to equestrian camp. Kate had invited the girls to go horseback riding instead. Hanna proves to be somewhat ignorant in front of Kate, though Kate corrects her. She introduces the girls to her two friends, Elizabeth ("Bitsy") and Margaux. After they mount their horses, Mona and Hanna lag behind while the other three go ahead. Later, after losing their horses and apparently getting bitten, the girls return to the stable. There, Hanna expresses to Mona her feelings that Kate and her friends were nasty towards her and also considered Hanna clueless. Mona suggests that Hanna wasn't trying hard enough, making Hanna really rail against her future step family and Kate's friends, calling the latter bitches who can go to hell. It turns out that Kate and her friends outside the stable overheard the whole exchange after Mona 'accidentally' set her riding helmet on the loudspeaker switch. The girls rush out to undo the damage, but Kate walks away miffed, with her friends at her heels.
Later, Hanna is afraid of getting into trouble with her father, but Kate surprises Hanna by not mentioning the incident to him. Instead, after Hanna thanks her for keeping quiet on the phone, she compares Hanna to a horse that will be broken. Her nasty side emerges, as she threatens to make Hanna's life miserable. Before hanging up, she welcomes Hanna to the family and sarcastically calls her "sis."
In "I Must Confess," Hanna tries to be nice to Kate, despite her threatening phone call and gives her a glossy picture books of horses. Kate agrees to put their differences behind them and start again. As Hanna and Kate are giving speeches later on, Kate suggests adding vodka to their drinks to calm their nerves. Hanna agrees, and soon gets very drunk.
Kate leaves Hanna alone in the bathroom with Isabel's wedding dress, and Hanna throws up on it before passing out. Tom is furious with Hanna for getting drunk and ruining Isabel's dress, thinking she is intentionally doing it, and doesn't believe her when she tries to explain. Kate returns after Tom leaves, but is surprised to see Hanna in Regina's company. Regina grabs Kate's purse and reveals that Kate had water bottles full of Vodka for Hanna and unspiked water bottles for herself, exposing Kate for setting up Hanna and trying to win over Tom's affections. Hanna vows revenge, though Kate just shrugs and walks away.
During the wedding in "Over My Dead Body," Kate greets Hanna and Caleb. Hanna walks away to answer her phone, and Kate tries to flirt with Caleb, who in return compliments Kate's dress before informing her that it shows off her back fat.
Tom announces in "Through Many Dangers, Toils, and Snares," that he will be moving back to Rosewood with Isabel and Kate in the near future.
Kate shows up at Rosewood High in "A Kiss Before Lying." Kate approaches the girls at the lunch table, looking a little nervous and awkwardly makes conversation with the girls. Spencer asks Kate if they have met before. Kate says it was at the wedding, but Spencer thinks it was somewhere else. Hanna shows Kate to her next class.
Later, the girls eat lunch with Kate, who is being uncharacteristically nice. Spencer asks Kate if she has ever been to Maine, along with many other questions, trying to figure out where they had met, clearly making Kate uncomfortable. When Kate leaves to meet her teachers, Hanna tells Spencer to back off because Kate might tell her dad her friends are grilling her.
The next day, everyone on Hanna's contacts list receives a photo of Kate, naked, changing in the locker room.
In "The Naked Truth," Hanna, Ashley, Isabel and Kate sit outside the Vice Principal's office in silence. Eventually, Vice Principal Tamborelli calls in Mrs. Marin, and both Isabel and Ashley respond. Isabel is furious about the situation and implies that Ashley is a bad mother, and that Hanna has it out for Kate. Ashley defends Hanna, while Isabel demands that Hanna be punished. Kate sits there looking hurt. Tamborelli assures them that Hanna will not be let off the hook, and under any other circumstances Hanna would be expelled, but due to the 'unusual' situation, he insists they attend the Rosewood High Truth Up Day, a guided workshop where students can own up to bad behavior and build barriers, until the school board decide what to do. Ashley volunteers to supervise.
Kate and Isabel are later seen talking to Vice Principal Tamborelli in the hallway, presumably to ask for a harsher punishment for Hanna.
In the courtyard, Hanna, Kate and Noel participate in an activity where they make suggestions on how to improve the school. Noel suggests hot tubs, and Kate simply says she wants to go back to her old school. Ella intervenes, asking for reasonable suggestions. She asks Kate what her old school has that Rosewood doesn't, and Kate simply says "nice people." Ella asks what else, and Kate says that students should have their own say, and if someone has messed with them, they should get to choose how to punish them, which Noel agrees to. He says that if someone messed with him, he would want payback, and explains how bad boys have nothing on mean girls, as a guy throws a few punches, whereas girls gang up on one another and don't fight fair, while glaring at Hanna. Hanna snaps back, saying Noel is the worst person in Rosewood, and seeing she has no allies, Hanna storms off.
In the hall, Aria, Hanna and Emily are sitting together eating dinner, when they notice Kate nearby. As Kate pulls off her sweater, Hanna notices a birthmark on Kate's waist. Realizing something, she looks at the picture of Kate on Emily's phone and sees that the birthmark isn't in the photo, which could mean it was Photoshopped. Hanna realizes Kate must have sent this photo out herself.
Hanna leads Kate into the girls bathroom and confronts her about the picture, saying she didn't take the picture, but she knows who did. Kate insists she doesn't know what Hanna is talking about, and Hanna says that there was no birthmark in the photo, and that Kate should be more careful when taking a sweater off in public. Kate yells at Hanna, saying that she had no choice, as she knew Spencer would download the hideous pictures of her at riding camp. Hanna asks Aria if she can borrow her phone, and Aria and Emily emerge from the bathroom stalls, having recorded the conversation and Kate's confession.
Hanna heads straight to Tamborelli to turn Kate in. Aria realizes how genius Kate's plan really was, had she not been caught. Isabel arrives at the school, worried about Kate. Ashley tells her that Tamborelli wanted to talk to Kate and Hanna alone first. Isabel asks if Hanna picked another fight, but Ashley says no, although she may have just ended the current one. Isabel is confused, and Ashley tells her that next time, before she points fingers, she should search her own family tree first for rotten fruits. Kate and Hanna leave Tamborelli's office, and Hanna hugs Ashley while Isabel stares at Kate in disbelief.
Kate has not been seen at school, nor mentioned, since "The Naked Truth," indicating that she may have been expelled for her prank.