Iiiiiii dunno, I haven't read the book and by your summary it doesn't seem like it's explicitly about rape anyway, but I think it's worth drawing a distinction between "she enjoys sex, so she's probably lying about being raped"--which is not a reasonable inference--and "she has a documented history of lying about everything, so she's probably lying about being raped"--which is. The former is the sort of thing that people are talking about when they talk about rape culture and believing women; with the latter, I reserve the right to take into account whether someone has lied to me repeatedly before when I'm deciding how seriously to take the things they're telling me now.