@Alhazred23: Even nonverbal communication still requires both side understand the 'language' being used.
Just look at real life pets, they have nonverbal communications that humans don't always understand.
Is a cat meowing because it want attention or is it hungry? Can you tell?
Is it nuzzling to you to mark its territory, or that's how it show it wants attention?
Also, Lila has been slowly studying the language.
She can understand a small amount of it, based on this moment.
https://mangadex.org/chapter/696181/17
It seems to imply that Lila spoke in their language just then.