A been-there-done-that, fifteen-year-old girl from the Big Apple, Daisy is our main chracter. She believes her life trajectory has been influenced by the unfortunate fact of "starting out your first day on the planet as a murderer" (1.5.8)—her mother died in childbirth—and that she might be able to "live quite happily without the labels I picked up because of it" (1.5.8). Poor girl.
Jaded by both her past and by her father's painful snubbing, Daisy compensates with sarcasm up the wazoo—at one point she says, "This Was the Life oh yes and Boy Had I Lucked Out" (1.7.7). It's a defense mechanism, really, keeping the world at bay so it doesn't hurt her anymore. Another defense mechanism is Daisy's habit of starving herself. In both her sarcasm and her starvation, we can see that she's been damaged by the first part of her life, and now does whatever she can to control her experience of the world.
Interestingly, despite her fondness for sarcasm and her general effort to keep people at arm's distance, Daisy's also honest to a fault, speaking her mind on topics that no one else would dare confess the truth about. For instance:
No matter how much you put on a sad expression and talked about how awful it was that all those people were killed and what about democracy and the Future of Our Great Nation the fact […] was that WE DIDN'T REALLY CARE. (1.9.19)
Yup, Daisy totally just admitted to not giving a poop about people dying—in the middle of wartime. This doesn't just show honesty, it shows she has hutzpah, too. Nothing wrong with that, right? Besides, it could be worse—as Daisy points out, she doesn't "get nearly enough credit in life for the things I manage not to say" (1.16.5). So while she's bold when she speaks, it's not like her mouth's a leaky faucet; she also reigns herself in.
Just like Daisy prides herself on knowing when to speak her mind and when to bite her tongue, she's also pretty self-aware as a narrator, admitting to things like the fact that she doesn't actually believe that "anyone with half a toehold in reality would think what we were doing was a good idea" (1.10.12). In other words, while she's recounting her story, she's also not so stuck inside her experience that she doesn't see it for what it is.
Part of this is the hindsight that comes from recounting a story after the fact, but Daisy's self-awareness extends to herself more generally and to how she comes across. For instance, she tells us: "I stuck with what I was good at, i.e., Blank bordering on Sullen" (1.14.4). And when comparing herself to Piper, Daisy realizes that "I didn't seem to have that effect on anyone but it would have been a waste for both of us to be saints" (1.22.15). In other words, she sees herself pretty clearly and doesn't try to make herself seem any better than she is.
Despite Daisy's lackadaisical and contemptuous attitude toward life, when push comes to shove, she'll have your back. So when she realizes she's become Piper's de facto guardian, she tells us:
[…] the thought made me fierce and strong like a mother wildebeest and all of a sudden I knew where people got the strength to pick up cars with babies lying under them. (1.15.10)
This is pretty instinctive, right? Like, Daisy doesn't have to think through this mama bear transformation, it just happens—it's something she already has deep inside her. And this makes it clear that while Daisy may not like too many people, those she does, she loves with a ferocious loyalty. For instance, she tells her younger cousin:
I would have to be buried alive in a ditch and stamped on by elephants before I would ever think that being anywhere with you wasn't a good thing SO THERE. (1.15.29)
Importantly, Daisy finds strength within herself to survive, not just for Piper and the others, but for herself, too. As we see her love and fight for other people, she starts doing the same for herself as well, which is particularly clear when she stops starving herself. In other words, as Daisy fights to keep Piper alive and to find her other cousins, she also starts fighting for herself, finding she possesses more strength than she ever realized. "I hated doing it but I COULD do it " (1.28.8), she notes—without any sarcasm at all. Looks like someone doesn't need her defense mechanisms quite so much anymore.