"What say we don't tell Lillian, eh? Let's keep it our little secret." (3.34)
It's one thing when your uncle asks you to keep a second helping of dessert a secret from your mother. A secret trip to Antarctica, though? That's something else entirely—and it's entirely not cool.
I kept trying to think what I'd say when Victor got back. About finding Mum's passport. Not that he would have taken it on purpose, of course. Of course not. (3.64)
Sym is trying to tell herself that Victor didn't take her mother's passport on purpose, but she doesn't sound terribly convinced. And with good reason, too; Victor definitely stole her mom's passport.
All he was sure of was that I shouldn't call my mother. In fact, every time I mentioned wanting to call her, he changed the subject, and that usually involved kissing. (10.57)
Sigurd isn't really romantically interested in Sym, but he needs to fool her so she doesn't call her mother.
"Mr. Bruch! Mr. Bruch, sir! Please!" begged Sigurd […]. (11.84)
Gee, we wonder why Sigurd is calling his father "Mr. Bruch." Oh wait—no we don't. It's definitely because Manfred isn't Sigurd's father. Duh.
"Except for a certain incontinuity of dialect," said Titus, but I shut my ears to him. (12.66)
When "Titus"—a.k.a. Sym's alter ego—says something unpleasant, she tries to ignore it. This may be the biggest evidence of the extent to which Sym deceived herself: She knows Titus is a figment of her imagination and only knows what she knows, and yet she ignores him anyway.
Thinking about it, I'd never once heard Sigurd and Manfred talk to each other in anything other than English. (13.33)
Q: How many red flags will Sym ignore before she realizes that Sigurd and Manfred aren't who they say they are? A: A lot. Like, a lot. Denial isn't just a river in Egypt.
"I'm sorry to break it to you, Victor, old man," he said loudly, calling from where he sat on the metal steps, "but I'm afraid I've been keeping you short on a few facts." (14.75)
When Manfred tells Victor he's "been keeping [him] short on a few facts," he means he's been lying his face off. In this regard, Manfred and Victor are kind of a match made in heaven—they both lie constantly.
"I find an obsessive with money to burn and I take it off him. It's what I do. I'm good!" (14.79)
Here Manfred finally admits to being a con man. Victor doesn't seem to care, though. Why's that? Oh, because he's been deceiving Manfred all along, too. Go team.
But he believed me, because he had learned better than to believe his eyes in Antarctica. (15.43)
In Antarctica, as in life, looks can be deceiving and seeing is not believing.
There again, everyone's capable of deception; that's another thing I've learned. (19.43)
It may be a cynical life lesson, but there's definitely some truth to Sym's understanding that "everyone's capable of deception." It takes her long enough to accept, but at least she has the rest of her life before her.