Or else she figured she'd play BOTH Sarah/S/Felix AND Nealon, and do everything to guarantee her escape, whichever party managed to make it happen first. That's the only way I can see in which her translation is legitimate and makes sense.

Yes, but Rachel was conning everyone with Nealon, so isn't her entire decoded "translation" totally suspect and probably bogus?

Yes, she played Catharine of Aragon, Queen of England and Henry VIII's first wife. Who was indeed Spanish, but not Queen of Spain. She was awesome as her.

BIG QUESTION (or am I missing something?): If Rachel and Nealon were double-crossing everyone from the beginning, then isn't her "translation" of the Dr. Moreau code completely suspect and probably made up? Is the book even written in her and her father's secret language at all? And since Rachel's credibility is gone,…

Actually, they use miles in the UK. More than 80% of the time. And stone, just because NO ONE ELSE DOES.

It can't be the US— she has a Canadian passport.

Not exactly cross-network, more inter-network: In the States, both Orphan Black and Dr. Who are carried by BBC America (or is that what you meant?).