Huh. You’re right. I guess I got that perception based on the fact that she also instantly understood Chewbacca. I don’t see how she would’ve had enough contact with droids or wookiees to understand either. Perhaps Rey’s is some kind of force connection while Poe’s is trained.
JEDIT: don’t see how Poe learning to understand BB-8 is any different from Han learning to understand Chewie.