Pretty cute, and yes, they are born like that! This is pretty much just babble, though it has a hint of structure. Scientists have observed deaf kids "babbling" with their hands, in something akin to sign language, so it's obviously inate. She's just practicing for the day when it all clicks in her mind and begins to make sense.
Reminds me of when I started learning German in HS. Yeah, most of us went through that "fun". But do you remember the night you DREAMT
in your new language, and you got most
of it right? I do, and that was a weird night for me. I'm a fairly lucid dreamer, so I kind of sat back and watched it play out, but in German! Wish I could have it again, but that was many years ago.