Bookworm: She is a huge fan of Gothic literature, but this doesn't necessarily make her smart or sensible. Rather the opposite, in some cases.
Break the Cutie: Catherine gets this treatment when she is pretty much thrown out of Northanger Abbey.
Cloud Cuckoo Lander: Catherine has a rather...er... 'odd' interpretation of the nuances of society - or rather an incredibly naive and innocent one: she doesn't think that anyone is capable of outright lying and manipulating other people and situations and could never do such a thing herself. To make matters worse, half the time her mind is with her Gothic Novels and a little departed from reality - with an unhealthy slab of Wrong Genre Savvy. In spite of this, or maybe because of it, she comes up with a lot of Armor-Piercing Questions that she'll ask A) without realising that they are in fact armor-piercing, and B) without realising that the questionee is extremely uncomfortable. She ends up feeling very confused when the person she's talking to suddenly changes the subject.
Country Mouse: She came from a rural home where everyone was rational and straightfoward. She becomes very confused by the hypocritical and egotistical behaviour she meets with in Bath.
Genre Savvy: But she knows quite a lot about the world of Gothic literature.
Heroic BSOD: After the General boots her out, the next days she spends at home are listless and unhappy, to her parents' concern.
The Ingenue: She can't even conceive of real people acting in a deceptive manner, which ill prepares her for dealing with the Thorpes.
Love at First Sight: She's attracted to Henry Tilney at their first meeting and spends much of the book wanting to get closer to him.
Love Triangle: Between Henry Tilney and John Thorpe, not that she's aware of the latter.
My God, What Have I Done?: After Henry points out how unjust her suspicions of General Tilney are, she's truly ashamed of herself and worries that she's lost his good opinion forever. She hasn't, but she still realizes she was wrong to treat the world like a novel.
Outdoorsy Gal: As a little girl, Catherine hated confinement and cleanliness, and loved rolling down the green slope at the back of the house. She liked playing cricket, baseball, riding on horseback, and running about the country. When she's grown-up, she still loves taking long walks and spending time outdoors and breathing fresh air.
Selective Obliviousness: Good grief. She's a fangirl of gothic novels and imagines things accordingly. But she misses the fact that her best friend, Eleanor, is the living embodiment of the stereotypical gothic heroine — estranged lover, dead mother, overbearing father, lives in an abbey with said father and the creatures of the forest, always wears white. Well, she notices but falsely assumes SHE'S the heroine (and is correct, just for the wrong book).
You Watch Too Much X: Henry tells her that she's been taking her novels way too seriously when he catches her snooping around Mrs. Tilney's old suite.
Bitch in Sheep's Clothing: Although she's quick to befriend Catherine and treat her as a sister, she has little regard for her feelings and disposes of the Morlands as soon as she sees more profitable prospects.
Bookworm: She and Catherine bond over books and eagerly discuss their progress through Udolpho.
Gold Digger: She throws over James Morland once she realizes he's not as rich as she supposed (and certainly not as much as the Tilneys).
Laser-Guided Karma: Isabella carelessly mistreats her fiance James by flirting with Captain Tilney. This results in James breaking the engagement, and it turns out that Captain Tilney is a careless flirt himself, meaning he's not about to propose to her.
That Liar Lies: After Captain Tilney loses interest, she writes to Catherine full of assurance that she still loves James, is Catherine's bestie, etcetera. At this point, Catherine sees through it.
Your Cheating Heart: An engagement is soon made between her and James Morland. But she shamelessly flirts with Captain Tilney, in front of James.
Gold Digger: Like his sister, he assumes the Morlands to be much richer than they actually are.
Know-Nothing Know-It-All: He chatters away on any subject as though he's an expert, such as Gothic lit (which Catherine has to correct him on).
Jerk Ass: Not only is he crude in manners, he's a shameless liar who tries to sabotage Catherine's acquaintance with the Tilneys and then misrepresents the family all over.
Malicious Slander: In high dudgeon over Catherine not accepting (or realizing) his proposal, he tells General Tilney that the Morlands are poor as churchmice.
Small Name, Big Ego: He's always inflating tales of his own adventures and prowess, and he's prone to exaggeration in general.
The Gadfly: He teases Catherine by playing up all the Gothic potential of the Abbey before telling her that it's actually a very pleasant building, but if he hadn't, she wouldn't have made such a big deal over the cabinet.
Genre Savvy: He's a fan of novels, which allows him to accurately guess what Catherine suspects about the death of his mother.
Nice Guy: Although he chastises her for her awful assumptions about the General, he never mentions the matter again.
What the Hell, Hero?: When he finds Catherine snooping around Mrs. Tilney's old rooms, he reminds her that they're living in civilized times, not a Gothic novel, and that just because the General isn't moping around the place doesn't mean he didn't grieve for Mrs. Tilney.
English Rose: A long-suffering English country gentry girl who is a beauty but makes no fuss about it, and is a great support to her father (who does not even appreciate her kindness) and has a loving and teasing relationship with her brother Henry.
Glurge Addict: A variation; she really enjoys history books over novels. Catherine doubts that any of the grand, inspiring speeches actually happened as written, but Eleanor enjoys them for what they are.
Lonely Rich Kid: She spends a lot of time in the abbey alone or in the pleasant company of the General. Henry even thanks Catherine for coming to stay, considering it a real favor to Eleanor, while Catherine is thrilled with the invitation and thinks she's the one who ought to feel grateful.
Sacred Hospitality: It falls to her to tell Catherine that she's being kicked out, and the task makes her miserable.
Abusive Parents: Obsessive and domineering, Catherine observes that when he leaves the Abbey, the mood of the place brightens considerably.
Parental Marriage Veto: Forbids Henry from seeing or thinking about Catherine again, thinking that she mislead them (when really, he was misguided by the Thorpes' assumptions and then slander). Henry defies this.
Sacred Hospitality: He violates this by turning Catherine out early in the morning and forcing her to undertake a 70-mile journey alone, shocking his children.