Jake made a deal with Fenestre–as long as he was inside his own house, he was safe from retribution.
Rachel knows that there are some things that only she and her cousin can do, and this is one of them.
We all know who did the arson at the end of Book 16.
Alternatively, the one where Jake and Rachel do terrible things because who else would be able to?
Which is honestly a genre of Animorphs fic I feel to be sadly lacking, but I digress.