there's something to be said about the standards rachel holds herself to and what she thinks her role in the team is.
like, yes: she's the "let's do it" person and most of the time it is because she really does want to do it, but here in #17 she's just forcing herself to go through with it even though she's very much uncomfortable with the mission. she can't let the cracks show, she knows, so she says "let's do it" almost subconsciously. especially when they were all about to dig the tunnel as moles and marco (teasingly) nominated her: she very much did not want to do it but she said she did — for her own sake and for the team's.
to me it's most evident in the marco books, but the rest of the team does see her as this sometimes crazy (insane, some might say), almost suicidal, almost enthusiastic, very ruthless girl who isn't afraid to go on the missions. it's a separate post why this is most evident in marco books (and the central point to that argument would be his description of her in #5), but the point is how they see her, and how she thinks they see her, and how she truly feels and what she doesn't want them to see.
there's another bit in #17 specifically. rachel saying that she needs cassie on a much deeper level. she needs cassie to hold up the morals and be the "good" one so that rachel can be "ruthless." i'm avoiding any spoilers for future moments in the series but this is, has been, and will be a recurring theme. rachel "hiding behind" her fellow animorphs, trying to pass herself off as just another one of them. rachel holding herself to those standards. rachel discovering who ("what") she is and deciding, right then and there, that no one can ever know the extent of it.
she's just rachel. the "let's do it" person. that's all that anyone can know.
