I've been waiting for this chapter for two weeks and I have to say it did pay off!
And about that last page... I think it hit her the fact that the series is already finished and she is probably thinking that if that's the case when she finishes reading the whole series and have the final chat about the ending then that's it, there won't be anything else connecting both of them anymore, that's why she got so sad all of a sudden.
Of course this is based on a hunch, though. Following her mindset it feels like she would just jump to such a rushed conclusion after getting this new data.